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Puberty is the process of physical changes through which a
child Biologically, a child (plural children) is a human being between the stages of childbirth, birth and puberty, or between the Development of the human body, developmental period of infancy and puberty. The legal definition of ''child'' generall ...

child
's
body Body may refer to: In science * Physical body, an object in physics that represents a large amount, has mass or takes up space * Body (biology), the physical material of an organism * Body plan, the physical features shared by a group of animals ...

body
matures into an
adult Biology, Biologically, an adult is an organism that has reached sexual maturity. In human context, the term ''adult'' has meanings associated with social and Law, legal concepts. In contrast to a "Minor (law), minor", a legal adult is a person ...

adult
body capable of
sexual reproduction Sexual reproduction is a type of reproduction Reproduction (or procreation or breeding) is the biological process Biological processes are those processes that are vital for an organism In biology, an organism (from Ancient Greek, ...
. It is initiated by
hormonal A hormone (from the Greek participle , "setting in motion") is any member of a class of signaling molecules in multicellular organisms, that are transported to distant organs to regulate physiology and / or behavior. Hormones are required for ...

hormonal
signals from the
brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tiss ...

brain
to the
gonad A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes (sex cells) and sex hormones of an organism. In the female of the species the reproductive cells are the egg cells, and in the male the reproductive cells are t ...
s: the
ovaries The ovary is an organ found in the female reproductive system 300px, 1. Labia_majora.html"_;"title="Vulva: 2. Labia_majora">Vulva: 2. Labia_majora; 3. Labia_minora; 4. Vulval_vestibule.html" "title="Labia_minora.html ...

ovaries
in a girl, the
testes Testicle or testis (plural testes) is the or in all animals, including humans. It is to the female . The functions of the testes are to produce both and , primarily . Testosterone release is controlled by the anterior pituitary , whereas ...

testes
in a boy. In response to the signals, the gonads produce hormones that stimulate
libido Libido (; colloquial Colloquialism or colloquial language is the style (sociolinguistics), linguistic style used for casual (informal) communication. It is the most common functional style of speech, the idiom normally employed in conversation ...
and the growth, function, and transformation of the brain,
bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa dubit ...

bone
s,
muscle Skeletal muscles (commonly referred to as muscles) are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly cat ...

muscle
,
blood Blood is a body fluid Body fluids, bodily fluids, or biofluids are liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isochoric flow) refers t ...

blood
,
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have differ ...

skin
,
hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Ph ...
,
breast The breast is one of two prominences located on the upper region of the of s. In females, it serves as the , which produces and secretes milk to feed s. Both females and males develop breasts from the same tissues. At , s, in conjunction ...

breast
s, and
sex organ A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis Testicle or testis (plural testes) is ...
s. Physical growth—height and weight—accelerates in the first half of puberty and is completed when an adult body has been developed. Before puberty, the external sex organs, known as primary sexual characteristics, are sex characteristics that distinguish boys and girls. Puberty leads to
sexual dimorphism Sexual dimorphism is the condition where the sex Sex is either of two divisions, typically male Male (♂) is the sex of an organism that produces the gamete known as sperm. A male gamete can fuse with a larger female gamete, or ovum, in ...
through the development of the
secondary sex characteristics Secondary sex characteristics are features that appear during puberty in humans, and at sexual maturity in other animals. These characteristics are particularly evident in the sexual dimorphism, sexually dimorphic phenotypic traits that distinguis ...
, which further distinguish the sexes. On average, girls begin puberty at ages 10–11 and complete puberty at ages 15–17; boys generally begin puberty at ages 11–12 and complete puberty at ages 16–17. The major landmark of puberty for females is
menarche Menarche ( ; ) is the first , or first , in female s. From both social and medical perspectives, it is often considered the central event of female , as it signals the possibility of . Girls experience menarche at different ages. Having menarc ...
, the onset of menstruation, which occurs on average between ages 12 and 13. For males, first
ejaculation Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the Male reproductive system, male reproductory tract as a result of an orgasm. It is the final stage and natural objective of male sexual stimulation, a ...

ejaculation
,
spermarche Spermarche—also known as semenarche—is the beginning of development of sperm Sperm is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive ...
, occurs on average at age 13.(Jorgensen & Keiding 1991). In the 21st century, the average age at which children, especially girls, reach puberty is lower compared to the 19th century, when it was 15 for girls and 17 for boys (with age at first periods for girls and voices break and growth spurt for boys being used as the age at onset). This can be due to any number of factors, including improved nutrition resulting in rapid body growth, increased weight and fat deposition, or exposure to
endocrine disruptor Endocrine disruptors, sometimes also referred to as hormonally active agents, endocrine disrupting chemicals, or endocrine disrupting compounds are chemicals that can interfere with endocrine (or hormonal A hormone (from the Greek participle ...
s such as
xenoestrogen Xenoestrogens are a type of xenohormoneXenohormones or environmental hormones are a group of compounds showing endocrine hormone A hormone (from the Greek participle , "setting in motion") is any member of a class of signaling molecules in mu ...
s, which can at times be due to food consumption or other environmental factors. Puberty which starts earlier than usual is known as
precocious puberty In medicine Medicine is the science Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity, awareness, or understanding of someone or something, such as facts ( descriptive knowledge), ...
, and puberty which starts later than usual is known as
delayed puberty Delayed puberty is when a person lacks or has incomplete development of specific sexual characteristics Sexual characteristics are physical or behavioral traits of an organism In biology, an organism (from Ancient Greek, Greek: ὀργαν ...
. Notable among the morphologic changes in size, shape, composition, and functioning of the pubertal body, is the development of secondary sex characteristics, the "filling in" of the child's body; from girl to woman, from boy to man. Derived from the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became ...

Latin
' (age of maturity), the word ''puberty'' describes the physical changes to sexual maturation, not the
psychosocial The psychosocial approach looks at individuals in the context of the combined influence that psychological factors and the surrounding social environment have on their physical and mental wellness and their ability to function. This approach is u ...
and cultural maturation denoted by the term ''adolescent development'' in
Western culture Western culture, also known as Western civilization, Occidental culture, or Western society, is the heritage Heritage may refer to: History and society * In history History (from Greek , ''historia'', meaning "inquiry; knowledge acquired ...
, wherein
adolescence Adolescence ()''Macmillan Dictionary for Students'' Macmillan, Pan Ltd. (1981), page 14, 456. Retrieved July 15, 2010. is a transitional stage of physical Physical may refer to: *Physical examination, a regular overall check-up with a doctor * ...
is the period of mental transition from childhood to
adult Biology, Biologically, an adult is an organism that has reached sexual maturity. In human context, the term ''adult'' has meanings associated with social and Law, legal concepts. In contrast to a "Minor (law), minor", a legal adult is a person ...

adult
hood, which overlaps much of the body's period of puberty.


Differences between male and female puberty

Two of the most significant differences between puberty in girls and puberty in boys are the age at which it begins, and the major
sex steroid Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is ...
s involved, the
androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typic ...
s and the
estrogen Estrogens or oestrogens, are a class of natural or synthetic s responsible for the development and regulation of the female and s. There are three major estrogens that have estrogenic hormonal activity: (E1), (E2), and (E3). Estradiol, an ...

estrogen
s. Although there is a wide range of normal ages, girls typically begin puberty around ages 10–11 and end puberty around 15–17; boys begin around ages 11–12 and end around 16–17. Girls attain reproductive maturity about four years after the first physical changes of puberty appear. In contrast, boys accelerate more slowly but continue to grow for about six years after the first visible pubertal changes.Garn, SM. Physical growth and development. In: Friedman SB, Fisher M, Schonberg SK., editors. Comprehensive Adolescent Health Care. St Louis: Quality Medical Publishing; 1992. Retrieved on 2009-02-20 Any increase in height beyond the post-pubertal age is uncommon. For boys, the
androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typic ...
testosterone Testosterone is the primary sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two cl ...
is the principal
sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typically made in the ...
; while testosterone is produced, all boys' changes are characterized as
virilization Virilization or masculinization is the biological development of adult male characteristics in young males or females. Most of the changes of virilization are produced by androgens. Virilization is most commonly used in three medical and Sex diffe ...
. A substantial product of testosterone metabolism in males is
estradiol Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous cycle, estrous and menstrual cycle, menstrual female reproductive cycles. Estradiol is resp ...

estradiol
. The conversion of testosterone to estradiol depends on the amount of body fat and estradiol levels in boys are typically much lower than in girls. The male "growth spurt" also begins later, accelerates more slowly, and lasts longer before the
epiphyses The epiphysis is the rounded end of a long bone, at its joint A joint or articulation (or articular surface) is the connection made between bones in the body which link the skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiol ...
fuse. Although boys are on average shorter than girls before puberty begins, adult men are on average about
taller Taller is a Communes of France, commune in the Landes (department), Landes Departments of France, department in Nouvelle-Aquitaine in southwestern France. William II Sánchez of Gascony perpetrated a major defeat of the Vikings at Taller in 982 ...
than women. Most of this sex difference in adult heights is attributable to a later onset of the growth spurt and a slower progression to completion, a direct result of the later rise and lower adult male levels of estradiol. The hormone that dominates female development is an
estrogen Estrogens or oestrogens, are a class of natural or synthetic s responsible for the development and regulation of the female and s. There are three major estrogens that have estrogenic hormonal activity: (E1), (E2), and (E3). Estradiol, an ...

estrogen
called
estradiol Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous cycle, estrous and menstrual cycle, menstrual female reproductive cycles. Estradiol is resp ...

estradiol
. While estradiol promotes growth of the breasts and
uterus The uterus (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...

uterus
, it is also the principal hormone driving the pubertal growth spurt and epiphyseal maturation and closure. Estradiol levels rise earlier and reach higher levels in women than in men. The hormonal maturation of females is considerably more complicated than in boys. The main
steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international ...
s, testosterone, estradiol, and
progesterone Progesterone (P4) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell (biology), cell. Endogenous substances and processes contrast with exo ...

progesterone
as well as
prolactin Prolactin (PRL), also known as lactotropin, is a protein best known for its role in enabling mammals (and birds), usually females, to lactation, produce milk. It is influential in over 300 separate processes in various vertebrates, including hu ...
play important physiological functions in puberty. Gonadal steroidgenesis in girls starts with production of testosterone which is typically quickly converted to estradiol inside the ovaries. However the rate of conversion from testosterone to estradiol (driven by FSH/LH balance) during early puberty is highly individual, resulting in very diverse development patterns of
secondary sexual characteristics Secondary sex characteristics are features that appear during puberty in human Humans (''Homo sapiens'') are the most populous and widespread species of primates, characterized by bipedality, opposable thumbs, hairlessness, and intelligence ...
. Production of progesterone in the ovaries begins with the development of ovulatory cycles in girls (during the lutheal phase of the cycle), before puberty low levels of progesterone are produced in the adrenal glands of both boys and girls.


Puberty onset

Puberty is preceded by
adrenarche Adrenarche is an early stage in sexual maturation that happens in some higher primates and in humans, typically peaks at around 20 years of age, and is eventually involved in the development of pubic hair, body odor, skin oiliness, and acne. Dur ...
, marking an increase of adrenal androgen production between ages 6–10. Adrenarche is sometimes accompanied by the early appearance of axillary and pubic hair. The first androgenic hair resulting from adrenarche can be also transient and disappear before the onset of true puberty. The onset of puberty is associated with high
GnRH Gonadotropin-releasing hormone (GnRH) is a releasing hormone Releasing hormones and inhibiting hormones are hormone A hormone (from the Greek participle , "setting in motion") is any member of a class of signaling molecules in multicellular ...
pulsing, which precedes the rise in sex hormones, LH and FSH. Exogenous GnRH pulses cause the onset of puberty. Brain tumors which increase GnRH output may also lead to premature puberty. The cause of the GnRH rise is unknown.
Leptin Leptin (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...

Leptin
might be the cause of the GnRH rise. Leptin has receptors in the
hypothalamus The hypothalamus (from Ancient Greek wikt:ὑπό, ὑπό, "under", and wikt:θάλαμος, θάλαμος, "chamber") is a portion of the brain that contains a number of small Nucleus (neuroanatomy), nuclei with a variety of functions. One of ...

hypothalamus
which synthesizes GnRH. Individuals who are deficient in leptin fail to initiate puberty. The levels of leptin increase with the onset of puberty, and then decline to adult levels when puberty is completed. The rise in GnRH might also be caused by genetics. A study discovered that a mutation in genes encoding both
neurokinin B Neurokinin B (NKB) belongs in the family of tachykinin peptides. Neurokinin B is implicated in a variety of human functions and pathways such as the secretion of gonadotropin-releasing hormone Gonadotropin-releasing hormone (GnRH) is a releasi ...

neurokinin B
as well as the neurokinin B receptor can alter the timing of puberty. The researchers hypothesized that neurokinin B might play a role in regulating the secretion of
kisspeptin Kisspeptins (including kisspeptin-54, formerly known as metastin) are proteins encoded by the ''KISS1'' gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance#History, Mende ...
, a compound responsible for triggering direct release of GnRH as well as indirect release of LH and FSH.


Effects of early and late puberty onset

Several studies about puberty have examined the effects of an early or a late onset of puberty in males and females. In general, girls who enter puberty late experience positive outcomes in adolescence and adulthood, while girls who enter puberty early experience negative outcomes. Boys who have earlier pubertal timing generally have more positive outcomes in adulthood but more negative outcomes in adolescence, while the reverse is true for later pubertal timing.


Girls

Outcomes have generally indicated that early onset of puberty in girls can be psychologically damaging. The main reason for this detrimental effect is the issue of
body image Body image is a person's thoughts, feelings and perception of the aesthetics or sexual attractiveness of their own body. The concept of body image is used in a number of disciplines, including psychology, medicine, psychiatry, psychoanalysis, phi ...

body image
. As they physically develop, gaining weight in several areas of the body, early-maturing girls usually look larger than girls who have not yet entered puberty. A result of the social pressure to be thin, the early-maturing girls develop a negative view of their body image. In addition, people may tease the girls about their visible breasts, forcing the early-maturing girl to hide her breasts by dressing differently. Embarrassment about a more developed body may also result in the refusal to undress for gym. These experiences lead to lower self-esteem, more depression and poorer body image in these early-maturing girls. Furthermore, as physical and emotional differences set them apart from people in their same age group, early-maturing girls develop relationships with older people. For instance, some early-maturing girls have older boyfriends, "attracted to the girls' womanly physique and girlish innocence." While having an older boyfriend might improve popularity among peers, it also increases the risk of alcohol and drug use, increased sexual relations (often unprotected), eating disorders and bullying. Generally, later onset of puberty in girls produces positive outcomes. They exhibit positive behaviors in adolescence that continue to adulthood.


Boys

In the past, early onset of puberty in boys has been associated with positive outcomes, such as leadership in high school and success in adulthood. However, recent studies have revealed that the risks and problems of early maturation in males might outweigh the benefits. Early-maturing boys develop "more aggressive, law-breaking, and alcohol abusing" behaviors, which result in anger towards parents and trouble in school and with the police. Early puberty also correlates with increased sexual activity and a higher instance of teenage pregnancy, both of which can lead to depression and other psychosocial issues. However, early puberty might also result in positive outcomes, such as popularity among peers, higher self-esteem and confidence, as a result of physical developments, such as taller height, developed muscles, muscular male breast and better athletic ability. On the other hand, late-maturing boys develop lower self-esteem and confidence and generally have lower popularity among peers, due to their less-developed physiques. Also, they experience problems with anxiety and depression and are more likely to be afraid of sex than other boys.


Changes in males

In boys, puberty begins with the enlargement of the testicles and scrotum. The penis also increases in size, and a boy develops pubic hair. A boy's testicles also begin making
sperm Sperm is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as ...

sperm
. The release of
semen Semen, also known as seminal fluid, is an organic fluid created to contain spermatozoon, spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphrodite, hermaphroditic animals and can fertilization, f ...

semen
, which contains sperm and other fluids, is called
ejaculation Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the Male reproductive system, male reproductory tract as a result of an orgasm. It is the final stage and natural objective of male sexual stimulation, a ...

ejaculation
. During puberty, a boy's erect penis becomes capable of ejaculating semen and impregnating a female. A boy's first ejaculation is an important milestone in his development. On average, a boy's first ejaculation occurs at age 13. Ejaculation sometimes occurs during sleep; this phenomenon is known as a
nocturnal emission A nocturnal emission, informally known as a wet dream, sex dream, nightfall or sleep orgasm, is a spontaneous orgasm Orgasm (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, ...
.


Testicular size

In boys, testicular enlargement is the first physical manifestation of puberty (and is termed gonadarche).
Testes Testicle or testis (plural testes) is the or in all animals, including humans. It is to the female . The functions of the testes are to produce both and , primarily . Testosterone release is controlled by the anterior pituitary , whereas ...

Testes
in prepubertal boys change little in size from about 1 year of age to the onset of puberty, averaging about 2–3 cm in length and about 1.5–2 cm in width. The size of the testicles is among the parameters of the Tanner scale for male genitals, from stage I which represents a volume of less than 1.5 ml, to stage V which represents a testicular volume of greater than 20 ml. Testicular size reaches maximal adult size about 6 years after the onset of puberty. While 18–20 cm3 is an average adult size, there is wide variation in testicular size in the normal population. After the boy's testicles have enlarged and developed for about one year, the length and then the breadth of the shaft of the
penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during Copulation (zoology), copulation. Such organs occur in many animals, both #Vertebrates, vertebrate ...

penis
will increase and the
glans penis The glans penis, commonly referred to as the glans, is a structure at the Anatomical terms of location#Proximal and distal, distal end of the penis in male mammals. It is the sensitive bulbous structure at the end of the human penis, and is ana ...

glans penis
and corpora cavernosa will also start to enlarge to adult proportions.


Male musculature and body shape

By the end of puberty, adult men have heavier
bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa dubit ...

bone
s and nearly twice as much skeletal
muscle Skeletal muscles (commonly referred to as muscles) are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly cat ...

muscle
. Some of the bone growth (e.g. shoulder width and jaw) is disproportionately greater, resulting in noticeably different male and female skeletal shapes. The average adult male has about 150% of the lean body mass of an average female, and about 50% of the body fat. This muscle develops mainly during the later stages of puberty, and muscle growth can continue even after boys are biologically adult. The peak of the so-called "strength spurt", the rate of muscle growth, is attained about one year after a male experiences his peak growth rate. Often, the fat pads of the male breast tissue and the male nipples will develop during puberty; sometimes, especially in one breast, this becomes more apparent and is termed
gynecomastia Gynecomastia (also spelled gynaecomastia) is the abnormal non-cancerous enlargement of one or both breasts in males due to the growth of breast tissue The breast is one of two prominences located on the upper ventral Standard anatomica ...

gynecomastia
. It is usually not a permanent phenomenon.


Erections

Erection An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis becomes firm, engorged, and enlarged. Penile erection is the result of a complex interaction of psychological, neural, vascular, ...

Erection
s during sleep or when waking up are medically known as
nocturnal penile tumescenceNocturnal penile tumescence is a spontaneous erection An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis becomes firm, engorged, and enlarged. Penile erection is the result of a co ...
and colloquially referred to as ''morning wood''. The penis can regularly get erect during sleep and men or boys often wake up with an erection. Once a boy reaches his
teenage Adolescence ()''Macmillan Dictionary for Students'' Macmillan, Pan Ltd. (1981), page 14, 456. Retrieved July 15, 2010. is a transitional stage of Developmental biology, physical and psychological Human development (biology), development that g ...
years, erections occur much more frequently due to puberty. Erections can occur spontaneously at any time of day, and if clothed may cause a bulge or "hump". This can be disguised or hidden by wearing close-fitting underwear, a long shirt and baggier clothes. Erections are common for male prepubescent children and infants, and can even occur before birth. Spontaneous erections are also known as involuntary or unwanted erections and are normal. Such erections can be embarrassing if they happen in public, such as a classroom or living room.


Foreskin retraction

During puberty, if not before, the tip and opening of a boy's
foreskin The foreskin is the double-layered fold of smooth muscle tissue, blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and ...
becomes wider, progressively allowing for retraction down the shaft of the
penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during Copulation (zoology), copulation. Such organs occur in many animals, both #Vertebrates, vertebrate ...

penis
and behind the
glans The glans (, plural "glandes" ; from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Thro ...

glans
, which ultimately should be possible without pain or difficulty. The membrane that bonds the inner surface of the foreskin with the glans disintegrates and releases the foreskin to separate from the glans. The foreskin then gradually becomes retractable. Research by Øster (1968) found that with the onset and continuation of puberty, the proportion of boys able to pull back their foreskins increased. At ages 12–13, Øster found that only 60% of boys were able to retract their foreskins; this increased to 85% by ages 14–15, and 95% by 16–17. He also found that 1% of those unable to fully retract experienced
phimosis Phimosis (from Greek language, Greek φίμωσις ''phimōsis'' 'muzzling'.) is a condition in which the ridged band of the ''Foreskin, akroposthion'' of the foreskin of the human penis, penis cannot stretch to allow it to be pulled back past th ...

phimosis
at ages 14–17, the remainder were partially able to. The findings were supported by further research by Kayaba ''et al'' (1996) on a sample of over 600 boys, and Ishikawa and Kawakita (2004) found that by age 15, 77% of their sample of boys could retract their foreskins. Beaugé (1997) reports that boys may assist the development of retractile foreskin by manual stretching. Once a boy is able to retract his foreskin, penile hygiene should become an important feature of his routine body care. Although the
American Academy of Pediatrics The American Academy of Pediatrics (AAP) is an American professional association of pediatricians, headquartered in Itasca, Illinois, Itasca, Illinois. It maintains its Department of Federal Affairs office in Washington, D.C. Background The Ac ...
states there is "little evidence to affirm the association between circumcision status and optimal penile hygiene", various studies suggest that boys be educated about the role of hygiene, including retracting the foreskin while urinating and rinsing under it and around the glans at each bathing opportunity. Regular washing under the foreskin was found by Krueger and Osborn (1986) to reduce the risk of numerous penile disorders, however Birley et al. (1993) report excessive washing with soap should be avoided because it dries the oils out of the tissues and can cause non-specific
dermatitis Dermatitis is inflammation of the Human skin, skin, typically characterized by itchiness, erythema, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become lichenification, thick ...

dermatitis
.


Pubic hair

Pubic hair Pubic hair is terminal body hair that is found in the genital area of adolescent and adult humans. The hair is located on and around the sex organs and sometimes at the top of the inside of the thighs. In the pubic region around the pubis ...

Pubic hair
often appears on a boy shortly after the genitalia begin to grow. The pubic hairs are usually first visible at the dorsal (abdominal) base of the penis. The first few hairs are described as stage 2. Stage 3 is usually reached within another 6–12 months, when the hairs are too many to count. By stage 4, the pubic hairs densely fill the "pubic triangle." Stage 5 refers to the spread of pubic hair to the
thigh In Outline of human anatomy, human anatomy, the thigh is the area between the hip (pelvis) and the knee. Anatomically, it is part of the Human leg, lower limb. The single bone in the thigh is called the femur. This bone is very thick and strong ...

thigh
s and upward towards the
navel The navel (clinically known as the umbilicus, commonly known as the belly button) is a protruding, flat, or hollowed area on the abdomen The abdomen (colloquially called the belly, tummy, midriff or stomach) is the part of the body between th ...

navel
as part of the developing
abdominal hair Abdominal hair is the hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which ...
.


Body and facial hair

In the months and years following the appearance of pubic hair, other areas of skin that respond to androgens may develop
androgenic hair Body hair, or androgenic hair, is the terminal hair In humans, terminal hair is thick and long, such as what grows on the scalp, as compared with vellus hair Vellus hair is short, thin, light-colored, and barely noticeable hair Hair is ...

androgenic hair
. The usual sequence is:
underarm The axilla (also, armpit, underarm or oxter) is the area on the human body directly under the joint A joint or articulation (or articular surface) is the connection made between bones in the body which link the skeletal system into a functional ...
(axillary) hair, perianal hair, ,
sideburn Sideburns, sideboards, or side whiskers are facial hair Facial hair is hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from ar ...

sideburn
(preauricular) hair, periareolar hair, and the
beard A beard is the hair that grows on the jaw, chin, upper lip, lower lip, cheeks, and neck of humans and some non-human animals. In humans, usually only pubescent or adult males are able to grow beards. Some women with hirsutism Hirsutism is ex ...

beard
area. As with most human biological processes, this specific order may vary among some individuals. Arm, leg,
chest The thorax or chest is a part of the anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανι ...
,
abdominal The abdomen (colloquially called the belly, tummy, midriff or stomach) is the part of the body between the thorax The thorax or chest is a part of the anatomy of humans, mammals, other tetrapod animals located between the neck and the abdomen. I ...
, and back hair become heavier more gradually. There is a large range in amount of body hair among adult men, and significant differences in timing and quantity of hair growth among different racial groups. Facial hair is often present in late adolescence, but may not appear until significantly later. Facial hair will continue to get coarser, darker and thicker for another 2–4 years after puberty. Some men do not develop full facial hair for up to 10 years after the completion of puberty. Chest hair may appear during puberty or years after, though not all men develop it.


Voice change and Adam's apple

Under the influence of androgens, the
larynx The larynx (), commonly called the voice box, is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist ...

larynx
(or voice box) grows in both sexes. This growth is far more prominent in boys, causing the male voice to drop and deepen, sometimes abruptly but rarely "overnight," about one
octave In music Music is the of arranging s in time through the of melody, harmony, rhythm, and timbre. It is one of the aspects of all human societies. General include common elements such as (which governs and ), (and its associated co ...

octave
, because the longer and thicker
vocal folds In humans, vocal cords, also known as vocal folds or voice reeds, are folds of tissue in the throat that are key in creating sounds through vocalization. The size of vocal cords affects the pitch of voice. Open when breathing and vibrating for ...

vocal folds
have a lower
fundamental frequency The fundamental frequency, often referred to simply as the fundamental, is defined as the lowest frequency Frequency is the number of occurrences of a repeating event per unit of time A unit of time is any particular time Time is th ...
. Before puberty, the larynx of boys and girls is about equally small. Occasionally, voice change is accompanied by unsteadiness of vocalization in the early stages of untrained voices. Most of the voice change happens during stage 3–4 of male puberty around the time of peak growth. Adult pitch is attained at an average age of 15 years, although the voice may not fully settle until early twenties. It usually precedes the development of significant facial hair by several months to years.


Changes in females


Breast development

The first physical sign of puberty in girls is usually a firm, tender lump under the center of the
areola The human areola (''areola mammae'', Entry "areola"
in
breast The breast is one of two prominences located on the upper region of the of s. In females, it serves as the , which produces and secretes milk to feed s. Both females and males develop breasts from the same tissues. At , s, in conjunction ...

breast
s, occurring on average at about 10.5 years of age.Marshall (1986), p. 187 This is referred to as
thelarche Thelarche is the onset of secondary breast development, which often represents the beginning of pubertal development. The initial growth of breasts occurs during fetal development in both males and females. Thelarche is the stage at which male and ...
. By the widely used
Tanner staging Tanner may refer to: * Tanner (occupation), the tanning of leather and hides People * Tanner (given name), * Tanner (surname), a surname (including a list of people with the name) *The Tanner Sisters, also referred to as "The Harbingers of Weirdn ...
of puberty, this is stage 2 of breast development (stage 1 is a flat, prepubertal breast). Within six to 12 months, the swelling has clearly begun in both sides, softened, and can be felt and seen extending beyond the edges of the areolae. This is stage 3 of breast development. By another 12 months (stage 4), the breasts are approaching mature size and shape, with areolae and
nipple The nipple is a raised region of tissue on the surface of the breast The breast is one of two prominences located on the upper region of the of s. In females, it serves as the , which produces and secretes milk to feed s. Both females ...

nipple
s forming a secondary mound. In most young women, this mound disappears into the contour of the mature breast (stage 5), although there is so much variation in sizes and shapes of adult breasts that stages 4 and 5 are not always separately identifiable.Marshall (1986), p. 188


Pubic hair

Pubic hair Pubic hair is terminal body hair that is found in the genital area of adolescent and adult humans. The hair is located on and around the sex organs and sometimes at the top of the inside of the thighs. In the pubic region around the pubis ...

Pubic hair
is often the second noticeable change in puberty, usually within a few months of thelarche. It is referred to as
pubarche Pubarche refers to the first appearance of pubic hair at puberty Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the ...
. The pubic hairs are usually visible first along the
labia The labia are part of the female genitalia; they are the major externally visible portions of the vulva. In humans, there are two pairs of labia: the ''labia majora'' (or the outer labia) are larger and thicker, while the ''labia minora'' are fold ...
. The first few hairs are described as Tanner stage 2. Stage 3 is usually reached within another 6–12 months, when the hairs are too numerous to count and appear on the as well. By stage 4, the pubic hairs densely fill the "pubic triangle." Stage 5 refers to spread of pubic hair to the
thigh In Outline of human anatomy, human anatomy, the thigh is the area between the hip (pelvis) and the knee. Anatomically, it is part of the Human leg, lower limb. The single bone in the thigh is called the femur. This bone is very thick and strong ...

thigh
s and sometimes as
abdominal hair Abdominal hair is the hair Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which ...
upward towards the
navel The navel (clinically known as the umbilicus, commonly known as the belly button) is a protruding, flat, or hollowed area on the abdomen The abdomen (colloquially called the belly, tummy, midriff or stomach) is the part of the body between th ...

navel
. In about 15% of girls, the earliest pubic hair appears before breast development begins.


Vagina, uterus, ovaries

Perineal skin
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin Alpha-keratin, or α-keratin, is a type of keratin Keratin () is one of a family of fibrous structural proteins known as Scleroprot ...

keratin
izes due to effect of estrogen increasing its resistance to infection. The
mucosal A mucous membrane or mucosa is a membrane Image:Schematic size.jpg, up150px, Schematic of size-based membrane exclusion A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions ...
surface File:Water droplet lying on a damask.jpg, Water droplet lying on a damask. Surface tension is high enough to prevent floating below the textile. A surface, as the term is most generally used, is the outermost or uppermost layer of a physical obje ...
of the vagina also changes in response to increasing levels of
estrogen Estrogens or oestrogens, are a class of natural or synthetic s responsible for the development and regulation of the female and s. There are three major estrogens that have estrogenic hormonal activity: (E1), (E2), and (E3). Estradiol, an ...

estrogen
, becoming thicker and duller pink in color (in contrast to the brighter red of the prepubertal vaginal mucosa). Mucosa changes into a multilayered structure with superficial layer of squamous cells. Estrogen increase glycogen content in
vaginal epithelium In mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Female#Mammalian female, femal ...
, which in future plays important part in maintaining vaginal pH. Whitish secretions (physiologic
leukorrhea Leukorrhea or (leucorrhoea American and British English spelling differences, British English), also known as fluor albus, is a thick, whitish, yellowish or greenish vaginal discharge. It has also been referred to as "the whites". There are many ...
) are a normal effect of estrogen as well. In the two years following thelarche, the
uterus The uterus (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...

uterus
,
ovaries The ovary is an organ found in the female reproductive system 300px, 1. Labia_majora.html"_;"title="Vulva: 2. Labia_majora">Vulva: 2. Labia_majora; 3. Labia_minora; 4. Vulval_vestibule.html" "title="Labia_minora.html ...

ovaries
, and the in the ovaries increase in size.Marshall (1986), p. 186–7 The ovaries usually contain small follicular
cyst A cyst is a closed sac, having a distinct envelope and division Division or divider may refer to: Mathematics *Division (mathematics), the inverse of multiplication *Division algorithm, a method for computing the result of mathematical division ...
s visible by
ultrasound Ultrasound is s with higher than the upper audible limit of human . Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies from person to person and is appro ...
. Before puberty, uterine body to cervix ratio is 1:1; which increases to 2:1 or 3:1 after completion of pubertal period.


Menstruation and fertility

The first is referred to as
menarche Menarche ( ; ) is the first , or first , in female s. From both social and medical perspectives, it is often considered the central event of female , as it signals the possibility of . Girls experience menarche at different ages. Having menarc ...
, and typically occurs about two years after
thelarche Thelarche is the onset of secondary breast development, which often represents the beginning of pubertal development. The initial growth of breasts occurs during fetal development in both males and females. Thelarche is the stage at which male and ...
. The average age of menarche is 12.5 in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

United States
. Most American girls experience their first period at 11, 12 or 13, but some experience it earlier than their 11th birthday and others after their 14th birthday. In fact, anytime between 8 and 16 is normal. In
Canada Canada is a country in the northern part of North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, ...

Canada
, the average age of menarche is 12.72, and in the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use Britain as a synonym for the United Kingdom. Some prefer to use Britain as shorth ...

United Kingdom
it is 12.9. The time between menstrual periods (menses) is not always regular in the first two years after menarche.
Ovulation Ovulation is the release of egg An egg is the organic vessel containing the in which an develops until it can survive on its own, at which point the animal hatches. An egg results from of an . Most s, (excluding s), and lay eggs, alth ...

Ovulation
is necessary for
fertility Fertility is the capability to produce offspring through reproduction following the onset of sexual maturity. The fertility rate is the average number of children born by a female during her lifetime and is quantified Demography, demographicall ...
, but may or may not accompany the earliest menses. In postmenarchal girls, about 80% of the cycles were anovulatory in the first year after menarche, 50% in the third year and 10% in the sixth year. Initiation of ovulation after menarche is not inevitable. A high proportion of girls with continued irregularity in the menstrual cycle several years from menarche will continue to have prolonged irregularity and anovulation, and are at higher risk for reduced fertility.


Body shape, fat distribution, and body composition

During this period, also in response to rising levels of estrogen, the lower half of the
pelvis The pelvis (plural pelves or pelvises) is the lower part of the Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pel ...

pelvis
and thus
hips In vertebrate anatomy, hip (or "coxa"Latin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) in medical terminology) refers to either an anatomical region or a joint. The hip region is ...
widen (providing a larger
birth canal In mammal Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of t ...
). Fat tissue increases to a greater percentage of the body composition than in males, especially in the typical female distribution of breasts, hips, buttocks, thighs, upper arms, and pubis. Progressive differences in fat distribution as well as sex differences in local skeletal growth contribute to the typical female body shape by the end of puberty. On average, at 10 years, girls have 6% more body fat than boys.


Body odor and acne

Rising levels of
androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typic ...
s can change the
fatty acid In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during ...
composition of
perspiration Perspiration, also known as sweating, is the production of fluids secreted by the sweat gland Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin Skin is the layer of usually soft, fl ...
, resulting in a more "adult"
body odor Body odor is present in all animals, including humans Humans (''Homo sapiens'') are the most populous and widespread species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of ...
. This often precedes thelarche and pubarche by one or more years. Another androgen effect is increased secretion of oil (
sebum A sebaceous gland is a microscopic exocrine Exocrine glands are gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormone A hormone (from the Greek participle , "setting in motion") is a ...

sebum
) from the skin. This change increases the susceptibility to
acne Acne, also known as acne vulgaris, is a long-term skin condition A skin condition, also known as cutaneous condition, is any medical condition A disease is a particular abnormal condition that negatively affects the structure or ...

acne
, a skin condition that is characteristic of puberty.Rosenfield (2002) Acne varies greatly in its severity.


Visual and other effects of hormonal changes

In girls,
estradiol Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous cycle, estrous and menstrual cycle, menstrual female reproductive cycles. Estradiol is resp ...

estradiol
(the primary female sex hormone) causes thickening of lips and
oral mucosa The oral mucosa is the mucous membrane A mucous membrane or mucosa is a biological membrane, membrane that lines various cavities in the body and covers the surface of internal organs. It consists of one or more layers of Epithelium, epithelial c ...

oral mucosa
as well as further development of the
vulva The vulva (plural: vulvas or vulvae; derived from Latin for wrapper or covering) consists of the external . The vulva includes the (or mons veneris), , , , , , , the , , and and vestibular s. The urinary meatus is also included as it opens ...

vulva
. In the vulva and vagina, estradiol causes thickening (
stratification Stratification may refer to: In mathematics: * Stratification (mathematics), any consistent assignment of numbers to predicate symbols * Stratified sampling , Data stratification in statistics In earth sciences: * Stable and unstable stratificati ...

stratification
) of the skin and the growth of both the myoepithelial layer and the
smooth muscle Smooth muscle is an involuntary non-striated muscle Striated muscle tissue is a muscle tissue Muscle tissue is a soft tissue that composes muscles in animal bodies, and gives rise to muscles' ability to contract. It is also referred to as myo ...

smooth muscle
of the vagina. Typically estradiol will also cause pronounced growth of the
labia minora The labia minora (Latin for ''smaller lips,'' singular: ''labium minus'' "smaller lip"), also known as the inner labia, inner lips, vaginal lips or nymphae, are two flaps of skin on either side of the human Humans (''Homo sapiens'') are the m ...

labia minora
and to a lesser degree of the
labia majora The labia majora (singular: ''labium majus'') are two prominent longitudinal Longitudinal is a geometric term of location which may refer to: * Longitude ** Line of longitude, also called a meridian (geography), meridian * Longitudinal engine, an ...

labia majora
. Estradiol is also responsible for the increased production of
pheomelanin Melanin (; from el, μέλας ''melas'', "black, dark") is a broad term for a group of natural pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at ...
, resulting in the characteristic red color of the lips, labia minora and sometimes labia majora. Estradiol together with other ovarian steroids also cause the darker coloration of the
areola The human areola (''areola mammae'', Entry "areola"
in
clitoris The clitoris ( or ) is a female sex organ A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the te ...

clitoris
and possibly has important effects on the growth and maturation of the
vestibular bulbs In female anatomy, the vestibular bulbs, bulbs of the vestibule or clitoral bulbs are two elongated masses of erectile tissue typically described as being situated on either side of the vaginal opening. They are united to each other in front by a ...
, corpus cavernosum of the clitoris and
urethral sponge The urethral sponge is a spongy cushion of tissue, found in the lower genital area of females, that sits against both the pubic bone and vaginal wall, and surrounds the urethra. Functions The urethral sponge is composed of erectile tissue; du ...
. Changes of the vulva initiated by estradiol as well as its direct effects also appear to influence the functioning of the lower urinary tract.


Underarm hair

Hair growth develops under the arms, starting out sparse before thickening and darkening over time.


Variations

In a general sense, the conclusion of puberty is reproductive maturity. Criteria for defining the conclusion may differ for different purposes: attainment of the ability to reproduce, achievement of maximal adult height, maximal gonadal size, or adult sex hormone levels. Maximal adult height is achieved at an average age of 15 years for an average girl and 18 years for an average boy. Potential fertility (sometimes termed ''nubility'') usually precedes completion of growth by 1–2 years in girls and 3–4 years in boys. Stage 5 typically represents maximal gonadal growth and adult hormone levels.


Age of onset

The definition of the onset of puberty may depend on perspective (e.g., hormonal versus physical) and purpose (establishing population normal standards, clinical care of early or late pubescent individuals, etc.). A common definition for the onset of puberty is physical changes to a person's body. These physical changes are the first visible signs of neural, hormonal, and gonadal function changes. The age at which puberty begins varies between individuals; usually, puberty begins between 10 and 13 years of age. The age at which puberty begins is affected by both genetic factors and by environmental factors such as nutritional state and social circumstances. An example of social circumstances is the Vandenbergh effect; a juvenile female who has significant interaction with adult males will enter puberty earlier than juvenile females who are not socially overexposed to adult males. The average age at which puberty begins may be affected by race as well. For example, the average age of
menarche Menarche ( ; ) is the first , or first , in female s. From both social and medical perspectives, it is often considered the central event of female , as it signals the possibility of . Girls experience menarche at different ages. Having menarc ...
in various populations surveyed has ranged from 12 to 18 years. The earliest average onset of puberty is for African-American girls and the latest average onset for high altitude subsistence populations in Asia. However, much of the higher age averages reflect nutritional limitations more than genetic differences and can change within a few generations with a substantial change in diet. The median age of menarche for a population may be an index of the proportion of undernourished girls in the population, and the width of the spread may reflect unevenness of wealth and food distribution in a population. Researchers have identified an earlier age of the onset of puberty. However, they have based their conclusions on a comparison of data from 1999 with data from 1969. In the earlier example, the sample population was based on a small sample of white girls (200, from Britain). The later study identified as puberty as occurring in 48% of African-American girls by age nine, and 12% of white girls by that age. One possible cause of a delay in the onset of puberty past the age 14 in girls and 15 in boys is
Kallmann syndrome Kallmann syndrome (KS) is a genetic disorder that prevents a person from starting or fully completing puberty Puberty is the process of physical changes through which a child Biologically, a child (plural children) is a human Hum ...
, a form of
hypogonadotropic hypogonadism Hypogonadotropic hypogonadism (HH), is due to problems with either the hypothalamus The hypothalamus (from Ancient Greek wikt:ὑπό, ὑπό, "under", and wikt:θάλαμος, θάλαμος, "chamber") is a portion of the brain that contains ...
(HH). Kallmann syndrome is also associated with a lack of sense of smell (
anosmia Anosmia, also known as smell blindness, is the loss of the ability to detect one or more smells. Anosmia may be temporary or permanent. It differs from hyposmia Hyposmia, or microsmia, is a reduced ability to smell and to detect odors. A related ...

anosmia
). Kallmann syndrome and other forms of HH affect both men and women. It is caused by a failure in
HPG axisHPG may refer to: * Huppuguda railway station, in Hyderabad, India * Hypothalamic–pituitary–gonadal axis * People's Defence Forces (Kurdish: '), the armed wing of the Kurdistan Workers' Party * Shennongjia Hongping Airport, in Hubei, China * Her ...
at puberty which results in low or zero
gonadotropin Gonadotropins are glycoprotein hormones secreted by gonadotropic cells of the anterior pituitary A major Organ (anatomy), organ of the endocrine system, the anterior pituitary (also called the adenohypophysis or pars anterior) is the glandular ...
( LH and FSH) levels with the subsequent result of a failure to commence or complete puberty, secondary
hypogonadism Hypogonadism means diminished functional activity of the gonad A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes (sex cells) and sex hormones of an organism. In the female of the species the reproductive cell ...
and
infertility Infertility is the inability of a person, animal or plant to Sexual reproduction, reproduce by natural means. It is usually not the natural state of a healthy adult, except notably among certain eusocial species (mostly haplodiploid insects). I ...
. Comparison of two individual with vast difference in the age of onset of puberty :


Historical shift

The average age at which the onset of puberty occurs has dropped significantly since the 1840s. In every decade from 1840 to 1950 there was a drop of four months in the average age of menarche among Western European females. In
Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål (, ; literally "book tongue") is an official written standard for the Norwegian language Norwegian (Norwegian: ''norsk'') is a Nort ...

Norway
, girls born in 1840 had their menarche at an average age of 17 years. In France, the average in 1840 was 15.3 years. In
England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest of England and the Celtic Sea to the southwest. E ...

England
, the average in 1840 was 16.5 years. In
Japan Japan ( ja, 日本, or , and formally ) is an island country An island country or an island nation is a country A country is a distinct territory, territorial body or political entity. It is often referred to as the land of an in ...

Japan
the decline happened later and was then more rapid: from 1945 to 1975 in Japan there was a drop of 11 months per decade. A 2006 study in Denmark found that puberty, as evidenced by breast development, started at an average age of 9 years and 10 months, a year earlier than when a similar study was done in 1991. Scientists believe the phenomenon could be linked to obesity or exposure to chemicals in the food chain, and is putting girls at greater long-term risk of breast cancer.


Genetic influence and environmental factors

Various studies have found direct genetic effects to account for at least 46% of the variation of timing of puberty in well-nourished populations. The genetic association of timing is strongest between mothers and daughters. The specific
gene In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mecha ...

gene
s affecting timing are not yet known. Among the candidates is an
androgen receptor The androgen receptor (AR), also known as NR3C4 (nuclear receptor subfamily 3, group C, member 4), is a type of nuclear receptor In the field of molecular biology, nuclear receptors are a class of proteins found within cells that are responsi ...

androgen receptor
gene. Researchers have hypothesized that early puberty onset may be caused by certain hair care products containing estrogen or placenta, and by certain chemicals, namely
phthalate Phthalates (, ), or phthalate esters, are ester An ester is a derived from an (organic or inorganic) in which at least one –OH group is replaced by an –O– () group, as in the substitution reaction of a and an . s are s of ; they are ...

phthalate
s, which are used in many cosmetics, toys, and plastic food containers. If genetic factors account for half of the variation of pubertal timing, environment factors are clearly important as well. One of the first observed environmental effects is that puberty occurs later in children raised at higher altitudes. The most important of the environmental influences is clearly nutrition, but a number of others have been identified, all which affect timing of female puberty and menarche more clearly than male puberty.


Hormones and steroids

There is theoretical concern, and animal evidence, that environmental hormones and
chemical A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which ...

chemical
s may affect aspects of prenatal or postnatal sexual development in humans. Large amounts of incompletely metabolized estrogens and
progestogen Progestogens, also sometimes written progestagens or gestagens, are a class of natural or synthetic steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 c ...
s from pharmaceutical products are excreted into the sewage systems of large cities, and are sometimes detectable in the environment.
Sex steroid Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is ...
s are sometimes used in cattle farming but have been banned in chicken meat production for 40 years. Although agricultural laws regulate use to minimize accidental human consumption, the rules are largely self-enforced in the United States. Significant exposure of a child to hormones or other substances that activate estrogen or androgen s could produce some or all of the changes of puberty. Harder to detect as an influence on puberty are the more diffusely distributed environmental chemicals like PCBs (
polychlorinated biphenyl A polychlorinated biphenyl (PCB) is an organic chlorine compound with the formula C12H10−''x''Cl''x''. Polychlorinated biphenyls were once widely deployed as dielectric A dielectric (or dielectric material) is an electrical insulator th ...
), which can bind and trigger estrogen receptors. More obvious degrees of partial puberty from direct exposure of young children to small but significant amounts of pharmaceutical sex steroids from exposure at home may be detected during medical evaluation for
precocious puberty In medicine Medicine is the science Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity, awareness, or understanding of someone or something, such as facts ( descriptive knowledge), ...
, but mild effects and the other potential exposures outlined above would not.
Bisphenol A Bisphenol A (BPA) is an organic compound#Synthetic compounds, organic synthetic compound with the chemical formula (CH3)2C(C6H4OH)2 belonging to the group of diphenylmethane derivatives and bisphenols, with two hydroxyphenyl Functional group, gro ...

Bisphenol A
(BPA) is a chemical used to make plastics, and is frequently used to make baby bottles, water bottles, sports equipment, medical devices, and as a coating in food and beverage cans. Scientists are concerned about BPA's behavioral effects on fetuses, infants, and children at current exposure levels because it can affect the prostate gland, mammary gland, and lead to early puberty in girls. BPA mimics and interferes with the action of estrogen—an important reproduction and development regulator. It leaches out of plastic into liquids and foods, and the
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services The United States Department of Heal ...
(CDC) found measurable amounts of BPA in the bodies of more than 90 percent of the U.S. population studied. The highest estimated daily intakes of BPA occur in infants and children. Many plastic baby bottles contain BPA, and BPA is more likely to leach out of plastic when its temperature is increased, as when one warms a baby bottle or warms up food in the microwave.


Nutritional influence

Nutrition Nutrition is the biochemical Biochemistry or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: st ...
al factors are the strongest and most obvious environmental factors affecting timing of puberty. Girls are especially sensitive to nutritional regulation because they must contribute all of the nutritional support to a growing fetus. Surplus
calorie The calorie is a unit of energy Unit may refer to: Arts and entertainment * UNIT Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the science fiction television series ''Doctor Who'' * Unit of action, a di ...
s (beyond growth and activity requirements) are reflected in the amount of
body fat Adipose tissue, body fat, or simply fat is a loose connective tissue Connective tissue is one of the four basic types of animal tissue (biology), tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesod ...
, which signals to the brain the availability of resources for initiation of puberty and fertility. Much evidence suggests that for most of the last few centuries, nutritional differences accounted for majority of variation of pubertal timing in different populations, and even among social classes in the same population. Recent worldwide increased consumption of animal protein, other changes in nutrition, and increases in childhood obesity have resulted in falling ages of puberty, mainly in those populations with the higher previous ages. In many populations the amount of variation attributable to nutrition is shrinking. Although available dietary energy (simple calories) is the most important dietary influence on timing of puberty, quality of the diet plays a role as well. Lower
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
intakes and higher
dietary fiber Dietary fiber (British spelling fibre) or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzyme Digestive may refer to: Biology *Digestion Digestion is the breakdown of large insolub ...
intakes, as occur with typical
vegetarian dietVegetarian diet may refer to: *Vegetarianism *Vegetarian cuisine *Plant-based diet (i.e., not necessarily stemming from vegetarian beliefs) *Veganism {{Disambig ...
s, are associated with later onset and slower progression of female puberty.


Obesity influence and exercise

Scientific researchers have linked early
obesity Obesity is a medical condition A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not due to any immediate external injury. ...

obesity
with an earlier onset of puberty in girls. They have cited obesity as a cause of breast development before nine years and menarche before twelve years. Early puberty in girls can be a harbinger of later health problems. The average level of daily physical activity has also been shown to affect timing of puberty, especially in females. A high level of exercise, whether for athletic or body image purposes, or for daily subsistence, reduces energy calories available for reproduction and slows puberty. The exercise effect is often amplified by a lower body fat mass and cholesterol.


Physical and mental illness

Chronic diseases can delay puberty in both boys and girls. Those that involve chronic inflammation or interfere with nutrition have the strongest effect. In the western world,
inflammatory bowel disease Inflammatory bowel disease (IBD) is a group of inflammation, inflammatory conditions of the colon (anatomy), colon and small intestine, Crohn's disease and ulcerative colitis being the principal types. Crohn's disease affects the small intestine an ...
and
tuberculosis Tuberculosis (TB) is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to the in ...

tuberculosis
have been notorious for such an effect in the last century, while in areas of the underdeveloped world, chronic
parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is adaptation (biology), adapted structurally to this w ...
infection An infection is the invasion of an organism's body by , their multiplication, and the reaction of tissues to the infectious agents and the s they produce. An infectious disease, also known as a transmissible disease or communicable disease, i ...

infection
s are widespread. Mental illnesses occur in puberty. The brain undergoes significant development by
hormone A hormone (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appr ...

hormone
s which can contribute to mood disorders such as
major depressive disorder Major depressive disorder (MDD), also known simply as depression, is a mental disorder A mental disorder, also called a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairm ...
,
bipolar disorder Bipolar disorder, previously known as manic depression, is a mental disorder A mental disorder, also called a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of ...

bipolar disorder
,
dysthymia Dysthymia, also known as persistent depressive disorder (PDD), is a mood disorder consisting of the same cognitive and physical problems as Major depressive disorder, depression, but with longer-lasting symptoms. The concept was coined by Robert ...
and
schizophrenia Schizophrenia is a mental disorder A mental disorder, also called a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. Such features may b ...

schizophrenia
. Girls aged between 15 and 19 make up 40% of
anorexia nervosa Anorexia nervosa, often referred to simply as anorexia, is an eating disorder An eating disorder is a mental disorder defined by abnormal eating behaviors that negatively affect a person's health, physical or mental health, mental health. On ...
cases.


Stress and social factors

Some of the least understood environmental influences on timing of puberty are social and psychological. In comparison with the effects of genetics, nutrition, and general health, social influences are small, shifting timing by a few months rather than years. Mechanisms of these social effects are unknown, though a variety of physiological processes, including
pheromone A pheromone (from Ancient Greek ' "to bear" and hormone) is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the s ...

pheromone
s, have been suggested based on animal research. The most important part of a child's psychosocial environment is the family, and most of the social influence research has investigated features of family structure and function in relation to earlier or later female puberty. Most of the studies have reported that menarche may occur a few months earlier in girls in high-stress households, whose fathers are absent during their early childhood, who have a stepfather in the home, who are subjected to prolonged
sexual abuse Sexual abuse, also referred to as molestation, is abusive sexual behavior Human sexual activity, human sexual practice or human sexual behaviour is the manner in which humans experience and express their Human sexuality, sexuality. Peop ...
in childhood, or who are
adopted Adoption is a process whereby a person assumes the parenting Parenting or child rearing promotes and supports the physical, emotion Emotions are biological states associated with all of the nerve systems brought on by neurophysiological ...
from a developing country at a young age. Conversely, menarche may be slightly later when a girl grows up in a large family with a biological father present. More extreme degrees of environmental stress, such as wartime refugee status with threat to physical survival, have been found to be associated with delay of maturation, an effect that may be compounded by dietary inadequacy. Most of these reported social effects are small and our understanding is incomplete. Most of these "effects" are statistical associations revealed by
epidemiologic Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and risk factor, determinants of health and disease conditions in defined populations. It is a cornerstone of public health, and shapes policy decisions ...
surveys. Statistical associations are not necessarily causal, and a variety of covariables and alternative explanations can be imagined. Effects of such small size can never be confirmed or refuted for any individual child. Furthermore, interpretations of the data are politically controversial because of the ease with which this type of research can be used for political advocacy. Accusations of bias based on political agenda sometimes accompany scientific criticism. Another limitation of the social research is that nearly all of it has concerned girls, partly because female puberty requires greater physiologic resources and partly because it involves a unique event (menarche) that makes survey research into female puberty much simpler than male. More detail is provided in the
menarche Menarche ( ; ) is the first , or first , in female s. From both social and medical perspectives, it is often considered the central event of female , as it signals the possibility of . Girls experience menarche at different ages. Having menarc ...
article.


Variations of sequence

The sequence of events of pubertal development can occasionally vary. For example, in about 15% of boys and girls,
pubarche Pubarche refers to the first appearance of pubic hair at puberty Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the ...
(the first pubic hairs) can precede, respectively, gonadarche and
thelarche Thelarche is the onset of secondary breast development, which often represents the beginning of pubertal development. The initial growth of breasts occurs during fetal development in both males and females. Thelarche is the stage at which male and ...
by a few months. Rarely,
menarche Menarche ( ; ) is the first , or first , in female s. From both social and medical perspectives, it is often considered the central event of female , as it signals the possibility of . Girls experience menarche at different ages. Having menarc ...
can occur before other signs of puberty in a few girls. These variations deserve medical evaluation because they can occasionally signal a disease.


Neurohormonal process

The endocrine
reproductive Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual orga ...
system consists of the
hypothalamus The hypothalamus (from Ancient Greek wikt:ὑπό, ὑπό, "under", and wikt:θάλαμος, θάλαμος, "chamber") is a portion of the brain that contains a number of small Nucleus (neuroanatomy), nuclei with a variety of functions. One of ...

hypothalamus
, the
pituitary In vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Hetero ...

pituitary
, the
gonad A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes (sex cells) and sex hormones of an organism. In the female of the species the reproductive cells are the egg cells, and in the male the reproductive cells are t ...
s, and the
adrenal gland The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer adrenal cortex ...

adrenal gland
s, with input and regulation from many other body systems. True puberty is often termed "central puberty" because it begins as a process of the
central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecu ...

central nervous system
. A simple description of hormonal puberty is as follows: #The brain's
hypothalamus The hypothalamus (from Ancient Greek wikt:ὑπό, ὑπό, "under", and wikt:θάλαμος, θάλαμος, "chamber") is a portion of the brain that contains a number of small Nucleus (neuroanatomy), nuclei with a variety of functions. One of ...

hypothalamus
begins to release pulses of
GnRH Gonadotropin-releasing hormone (GnRH) is a releasing hormone Releasing hormones and inhibiting hormones are hormone A hormone (from the Greek participle , "setting in motion") is any member of a class of signaling molecules in multicellular ...
. #Cells in the
anterior pituitary A major Organ (anatomy), organ of the endocrine system, the anterior pituitary (also called the adenohypophysis or pars anterior) is the glandular, Anatomical terms of location#Usage in human anatomy, anterior lobe that together with the Anatomic ...
respond by secreting LH and FSH into the circulation. #The
ovaries The ovary is an organ found in the female reproductive system 300px, 1. Labia_majora.html"_;"title="Vulva: 2. Labia_majora">Vulva: 2. Labia_majora; 3. Labia_minora; 4. Vulval_vestibule.html" "title="Labia_minora.html ...

ovaries
or
testes Testicle or testis (plural testes) is the or in all animals, including humans. It is to the female . The functions of the testes are to produce both and , primarily . Testosterone release is controlled by the anterior pituitary , whereas ...

testes
respond to the rising amounts of LH and FSH by growing and beginning to produce
estradiol Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous cycle, estrous and menstrual cycle, menstrual female reproductive cycles. Estradiol is resp ...

estradiol
and
testosterone Testosterone is the primary sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two cl ...
. #Rising levels of estradiol and testosterone produce the body changes of female and male puberty. The onset of this neurohormonal process may precede the first visible body changes by 1–2 years.


Components of the endocrine reproductive system

The
arcuate nucleus The arcuate nucleus of the hypothalamus (also known as ARH, ARC, or infundibular nucleus) is an aggregation of neuron A neuron or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections ...
of the
hypothalamus The hypothalamus (from Ancient Greek wikt:ὑπό, ὑπό, "under", and wikt:θάλαμος, θάλαμος, "chamber") is a portion of the brain that contains a number of small Nucleus (neuroanatomy), nuclei with a variety of functions. One of ...

hypothalamus
is the driver of the reproductive system. It has
neuron A neuron or nerve cell is an electrically excitable cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or re ...

neuron
s which generate and release pulses of GnRH into the portal venous system of the
pituitary gland upright=1.2, The Hypothalamus-Pituitary Complex. In vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingd ...

pituitary gland
. The arcuate nucleus is affected and controlled by neuronal input from other areas of the brain and hormonal input from the
gonad A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes (sex cells) and sex hormones of an organism. In the female of the species the reproductive cells are the egg cells, and in the male the reproductive cells are t ...
s,
adipose Adipose tissue, body fat, or simply fat is a loose connective tissue Connective tissue is one of the four basic types of animal tissue (biology), tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesod ...
tissue and a variety of other systems. The
pituitary gland upright=1.2, The Hypothalamus-Pituitary Complex. In vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingd ...

pituitary gland
responds to the pulsed GnRH signals by releasing LH and FSH into the blood of the general circulation, also in a pulsatile pattern. The gonads (
testes Testicle or testis (plural testes) is the or in all animals, including humans. It is to the female . The functions of the testes are to produce both and , primarily . Testosterone release is controlled by the anterior pituitary , whereas ...

testes
and
ovaries The ovary is an organ found in the female reproductive system 300px, 1. Labia_majora.html"_;"title="Vulva: 2. Labia_majora">Vulva: 2. Labia_majora; 3. Labia_minora; 4. Vulval_vestibule.html" "title="Labia_minora.html ...

ovaries
) respond to rising levels of LH and FSH by producing the
steroid A steroid is a biologically active organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the prope ...

steroid
sex hormones Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typically made in the ...
,
testosterone Testosterone is the primary sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two cl ...
and
estrogen Estrogens or oestrogens, are a class of natural or synthetic s responsible for the development and regulation of the female and s. There are three major estrogens that have estrogenic hormonal activity: (E1), (E2), and (E3). Estradiol, an ...

estrogen
. The
adrenal gland The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer adrenal cortex ...

adrenal gland
s are a second source for steroid hormones. Adrenal maturation, termed
adrenarche Adrenarche is an early stage in sexual maturation that happens in some higher primates and in humans, typically peaks at around 20 years of age, and is eventually involved in the development of pubic hair, body odor, skin oiliness, and acne. Dur ...
, typically precedes gonadarche in mid-childhood.


Major hormones

*
Neurokinin B Neurokinin B (NKB) belongs in the family of tachykinin peptides. Neurokinin B is implicated in a variety of human functions and pathways such as the secretion of gonadotropin-releasing hormone Gonadotropin-releasing hormone (GnRH) is a releasi ...

Neurokinin B
(a
tachykinin Tachykinin peptides are one of the largest families of neuropeptide Image:Neuropeptide Y.png, Neuropeptide Y Neuropeptides are small proteins produced by neurons that act on G protein-coupled receptors and are responsible for slow-onset, long-last ...
peptide Peptides (from Greek language Greek (modern , romanized: ''Elliniká'', Ancient Greek, ancient , ''Hellēnikḗ'') is an independent branch of the Indo-European languages, Indo-European family of languages, native to Greece, Cyprus, Albania, ...
) and
kisspeptin Kisspeptins (including kisspeptin-54, formerly known as metastin) are proteins encoded by the ''KISS1'' gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance#History, Mende ...
(a
neuropeptide Image:Neuropeptide Y.png, Neuropeptide Y Neuropeptides are small proteins produced by neurons that act on G protein-coupled receptors and are responsible for slow-onset, long-lasting modulation of synaptic transmission. Neuropeptides often coexist ...
), both present in
KNDy neuron Kisspeptin, neurokinin B, and dynorphin (KNDy) neurons are neurons in the hypothalamus of the brain that are central to the hormonal control of reproduction. KNDy neurons in the hypothalamus coexpress kisspeptin, neurokinin B (NKB) and dynorphin. ...
s of the
hypothalamus The hypothalamus (from Ancient Greek wikt:ὑπό, ὑπό, "under", and wikt:θάλαμος, θάλαμος, "chamber") is a portion of the brain that contains a number of small Nucleus (neuroanatomy), nuclei with a variety of functions. One of ...

hypothalamus
, are critical parts of the control system that switches on the release of GnRH at the start of puberty. *
GnRH Gonadotropin-releasing hormone (GnRH) is a releasing hormone Releasing hormones and inhibiting hormones are hormone A hormone (from the Greek participle , "setting in motion") is any member of a class of signaling molecules in multicellular ...
(
gonadotropin Gonadotropins are glycoprotein hormones secreted by gonadotropic cells of the anterior pituitary A major Organ (anatomy), organ of the endocrine system, the anterior pituitary (also called the adenohypophysis or pars anterior) is the glandular ...
-releasing hormone) is a
peptide Peptides (from Greek language Greek (modern , romanized: ''Elliniká'', Ancient Greek, ancient , ''Hellēnikḗ'') is an independent branch of the Indo-European languages, Indo-European family of languages, native to Greece, Cyprus, Albania, ...
hormone A hormone (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appr ...

hormone
released from the
hypothalamus The hypothalamus (from Ancient Greek wikt:ὑπό, ὑπό, "under", and wikt:θάλαμος, θάλαμος, "chamber") is a portion of the brain that contains a number of small Nucleus (neuroanatomy), nuclei with a variety of functions. One of ...

hypothalamus
which stimulates
gonadotrope Gonadotropic cells (called also Gonadotropes or Gonadotrophs or Delta Cells or Delta basophils) are endocrine The endocrine system is a messenger system comprising feedback loops of the hormone A hormone (from the Greek participle , "setting ...
cells of the anterior
pituitary In vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Hetero ...

pituitary
. * LH (luteinizing hormone) is a larger
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
hormone secreted into the general circulation by gonadotrope cells of the anterior
pituitary gland upright=1.2, The Hypothalamus-Pituitary Complex. In vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingd ...

pituitary gland
. The main target cells of LH are the
Leydig cell Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules Seminiferous tubules are located within the testes Testicle or testis (plural testes) is the male reproductive gland or gonad A go ...
s of
testes Testicle or testis (plural testes) is the or in all animals, including humans. It is to the female . The functions of the testes are to produce both and , primarily . Testosterone release is controlled by the anterior pituitary , whereas ...

testes
and the
theca cell In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...
s of the
ovaries The ovary is an organ found in the female reproductive system 300px, 1. Labia_majora.html"_;"title="Vulva: 2. Labia_majora">Vulva: 2. Labia_majora; 3. Labia_minora; 4. Vulval_vestibule.html" "title="Labia_minora.html ...

ovaries
. LH secretion changes more dramatically with the initiation of puberty than FSH, as LH levels increase about 25-fold with the onset of puberty, compared with the 2.5-fold increase of FSH. * FSH ( stimulating hormone) is another protein hormone secreted into the general circulation by the
gonadotrope Gonadotropic cells (called also Gonadotropes or Gonadotrophs or Delta Cells or Delta basophils) are endocrine The endocrine system is a messenger system comprising feedback loops of the hormone A hormone (from the Greek participle , "setting ...
cells of the anterior pituitary. The main target cells of FSH are the
ovarian follicle An ovarian follicle is a roughly spheroid cellular aggregation set found in the ovaries The ovary is an organ found in the female reproductive system 400px, 1. Labia_majora.html"_;"title="Vulva: 2. Labia_majora">Vulva: 2. Labia ...

ovarian follicle
s and the
Sertoli cell A Sertoli cell (a kind of sustentacular cell Micrograph highlighting the sustentacular cells in a paraganglioma. S100 protein">S100 immunostain A sustentacular cell is a type of cell primarily associated with structural support, they can be found ...
s and
spermatogenic Spermatogenesis is the process by which haploid Ploidy () is the number of complete sets of chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. Most eukaryotic chromosomes include p ...

spermatogenic
tissue of the
testes Testicle or testis (plural testes) is the or in all animals, including humans. It is to the female . The functions of the testes are to produce both and , primarily . Testosterone release is controlled by the anterior pituitary , whereas ...

testes
. *
Testosterone Testosterone is the primary sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two cl ...
is a
steroid A steroid is a biologically active organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the prope ...

steroid
hormone produced primarily by the
Leydig cell Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules Seminiferous tubules are located within the testes Testicle or testis (plural testes) is the male reproductive gland or gonad A go ...
s of the
testes Testicle or testis (plural testes) is the or in all animals, including humans. It is to the female . The functions of the testes are to produce both and , primarily . Testosterone release is controlled by the anterior pituitary , whereas ...

testes
, and in lesser amounts by the
theca cell In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...
s of the ovaries and the adrenal cortex. Testosterone is the primary mammalian
androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typic ...
and the "original"
anabolic steroid Anabolic steroids, also known more properly as anabolic–androgenic steroids (AAS), are steroid A steroid is a biologically active organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability t ...
. It acts on
androgen receptor The androgen receptor (AR), also known as NR3C4 (nuclear receptor subfamily 3, group C, member 4), is a type of nuclear receptor In the field of molecular biology, nuclear receptors are a class of proteins found within cells that are responsi ...

androgen receptor
s in responsive tissue throughout the body. *
Estradiol Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous cycle, estrous and menstrual cycle, menstrual female reproductive cycles. Estradiol is resp ...

Estradiol
is a
steroid A steroid is a biologically active organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the prope ...

steroid
hormone produced by
aromatization Aromatization is a chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical A chemical substance is a form of matter having constant che ...
of testosterone. Estradiol is the principal human
estrogen Estrogens or oestrogens, are a class of natural or synthetic s responsible for the development and regulation of the female and s. There are three major estrogens that have estrogenic hormonal activity: (E1), (E2), and (E3). Estradiol, an ...

estrogen
and acts on
estrogen receptor Estrogen receptors (ERs) are a group of proteins found inside cells. They are receptors that are activated by the hormone A hormone (from the Greek participle , "setting in motion") is any member of a class of signaling molecules in multice ...
s throughout the body. The largest amounts of estradiol are produced by the
granulosa cell A granulosa cell or follicular cell is a somatic cell A somatic cell (from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC ...
s of the
ovaries The ovary is an organ found in the female reproductive system 300px, 1. Labia_majora.html"_;"title="Vulva: 2. Labia_majora">Vulva: 2. Labia_majora; 3. Labia_minora; 4. Vulval_vestibule.html" "title="Labia_minora.html ...

ovaries
, but lesser amounts are derived from
testicular Testicle or testis (plural testes) is the male Male (♂) is the sex of an organism that produces the gamete known as sperm. A male gamete can fuse with a larger female gamete, or ovum, in the process of fertilization. A male cannot sexual r ...

testicular
and
adrenal The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex wh ...

adrenal
testosterone. *
Adrenal The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex wh ...

Adrenal
androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typic ...
s are steroids produced by the zona reticulosa of the
adrenal cortex The adrenal cortex is the outer region and also the largest part of an adrenal gland. It is divided into three separate zones: zona glomerulosa, zona fasciculata and zona reticularis. Each zone is responsible for producing specific hormones. It is a ...
in both sexes. The major adrenal androgens are
dehydroepiandrosterone Dehydroepiandrosterone (DHEA), also known as androstenolone, is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell (biology), cell. Endogenous ...

dehydroepiandrosterone
,
androstenedione Androstenedione, or 4-androstenedione (abbreviated as A4 or Δ4-dione), also known as androst-4-ene-3,17-dione, is an endogenous weak androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or syntheti ...

androstenedione
(which are precursors of testosterone), and dehydroepiandrosterone sulfate which is present in large amounts in the
blood Blood is a body fluid Body fluids, bodily fluids, or biofluids are liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isochoric flow) refers t ...

blood
. Adrenal androgens contribute to the androgenic events of early puberty in girls. *
IGF1 Insulin-like growth factor 1 (IGF-1), also called somatomedin C, is a hormone A hormone (from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, ...
(
insulin-like growth factor 1 Insulin-like growth factor 1 (IGF-1), also called somatomedin C, is a hormone similar in tertiary structure, molecular structure to insulin which plays an important role in childhood growth, and has Anabolism, anabolic effects in adults. IGF-1 is ...
) rises substantially during puberty in response to rising levels of
growth hormone Growth hormone (GH) or somatotropin, also known as human growth hormone (hGH or HGH) in its human form, is a peptide hormone that stimulates growth, cell (biology), cell reproduction, and cell regeneration in humans and other animals. It is th ...
and may be the principal mediator of the pubertal growth spurt. *
Leptin Leptin (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...

Leptin
is a protein hormone produced by
adipose tissue Adipose tissue, body fat, or simply fat is a loose connective tissue Connective tissue is one of the many basic types of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biolo ...

adipose tissue
. Its primary target organ is the
hypothalamus The hypothalamus (from Ancient Greek wikt:ὑπό, ὑπό, "under", and wikt:θάλαμος, θάλαμος, "chamber") is a portion of the brain that contains a number of small Nucleus (neuroanatomy), nuclei with a variety of functions. One of ...

hypothalamus
. The leptin level seems to provide the
brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tiss ...

brain
a rough indicator of adipose mass for purposes of regulation of
appetite Appetite is the desire to eat Eating (also known as consuming) is the ingestion of food Food is any substance consumed to provide nutritional support for an organism In biology, an organism (from Ancient Greek, Greek: ὀργα ...
and
energy metabolism Bioenergetics is a field in biochemistry Biochemistry or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three f ...
. It also plays a permissive role in female puberty, which usually will not proceed until an adequate body mass has been achieved.


Endocrine perspective

The becomes functional by the end of the first of fetal life. The testes and ovaries become briefly inactive around the time of birth but resume hormonal activity until several months after birth, when incompletely understood mechanisms in the brain begin to suppress the activity of the arcuate nucleus. This has been referred to as maturation of the prepubertal "gonadostat," which becomes sensitive to negative feedback by
sex steroid Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is ...
s. The period of hormonal activity until several months after birth, followed by suppression of activity, may correspond to the period of infant sexuality, followed by a
latency stage In his model of the child's psychosexual development In Freudian psychology Psychology is the science of mind and behavior. Psychology includes the study of consciousness, conscious and Unconscious mind, unconscious phenomena, as well as ...
, which
Sigmund Freud Sigmund Freud ( , ; born Sigismund Schlomo Freud; 6 May 1856 – 23 September 1939) was an Austrian and the founder of , a clinical method for treating through dialogue between a patient and a psychoanalyst. Freud was born to (from ) parents ...

Sigmund Freud
described.
Gonadotropin Gonadotropins are glycoprotein hormones secreted by gonadotropic cells of the anterior pituitary A major Organ (anatomy), organ of the endocrine system, the anterior pituitary (also called the adenohypophysis or pars anterior) is the glandular ...
and sex steroid levels fall to low levels (nearly undetectable by current clinical assays) for approximately another 8 to 10 years of childhood. Evidence is accumulating that the reproductive system is not totally inactive during the childhood years. Subtle increases in gonadotropin pulses occur, and ovarian follicles surrounding
germ cell A germ cell is any biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of all known organisms. Cells are the smallest units of life, and hence are often referred to a ...
s (future
egg An egg is the organic vessel containing the in which an develops until it can survive on its own, at which point the animal hatches. An egg results from of an . Most s, (excluding s), and lay eggs, although some, such as s, do not. eg ...

egg
s) double in number. Normal puberty is initiated in the hypothalamus, with de-inhibition of the pulse generator in the arcuate nucleus. This inhibition of the arcuate nucleus is an ongoing active suppression by other areas of the brain. The signal and mechanism releasing the arcuate nucleus from inhibition have been the subject of investigation for decades and remain incompletely understood.
Leptin Leptin (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...

Leptin
levels rise throughout childhood and play a part in allowing the arcuate nucleus to resume operation. If the childhood inhibition of the arcuate nucleus is interrupted prematurely by injury to the brain, it may resume pulsatile gonadotropin release and puberty will begin at an early age. Neurons of the arcuate nucleus secrete
gonadotropin releasing hormone Gonadotropin-releasing hormone (GnRH) is a releasing hormone Releasing hormones and inhibiting hormones are hormone A hormone (from the Greek participle , "setting in motion") is any member of a class of signaling molecules in multicellular ...
(GnRH) into the blood of the pituitary portal system. An American physiologist, Ernst Knobil, found that the GnRH signals from the hypothalamus induce pulsed secretion of LH (and to a lesser degree, FSH) at roughly 1-2 hour intervals. The LH pulses are the consequence of pulsatile GnRH secretion by the arcuate nucleus that, in turn, is the result of an
oscillator Oscillation is the repetitive variation, typically in time, of some measure about a central value (often a point of Mechanical equilibrium, equilibrium) or between two or more different states. The term ''vibration'' is precisely used to describe ...

oscillator
or signal generator in the central nervous system ("GnRH pulse generator"). In the years preceding physical puberty, Robert M. Boyar discovered that the gonadotropin pulses occur only during sleep, but as puberty progresses they can be detected during the day. By the end of puberty, there is little day-night difference in the amplitude and frequency of gonadotropin pulses. Some investigators have attributed the onset of puberty to a
resonance Resonance describes the phenomenon of increased amplitude The amplitude of a Periodic function, periodic Variable (mathematics), variable is a measure of its change in a single Period (mathematics), period (such as frequency, time or Wavelen ...

resonance
of oscillators in the brain. By this mechanism, the gonadotropin pulses that occur primarily at night just before puberty represent beats. An array of "autoamplification processes" increases the production of all of the pubertal hormones of the hypothalamus, pituitary, and gonads. Regulation of
adrenarche Adrenarche is an early stage in sexual maturation that happens in some higher primates and in humans, typically peaks at around 20 years of age, and is eventually involved in the development of pubic hair, body odor, skin oiliness, and acne. Dur ...
and its relationship to maturation of the hypothalamic-gonadal axis is not fully understood, and some evidence suggests it is a parallel but largely independent process coincident with or even preceding central puberty. Rising levels of adrenal
androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typic ...
s (termed adrenarche) can usually be detected between 6 and 11 years of age, even before the increasing gonadotropin pulses of hypothalamic puberty. Adrenal androgens contribute to the development of pubic hair (
pubarche Pubarche refers to the first appearance of pubic hair at puberty Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the ...
), adult
body odor Body odor is present in all animals, including humans Humans (''Homo sapiens'') are the most populous and widespread species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of ...
, and other androgenic changes in both sexes. The primary clinical significance of the distinction between adrenarche and gonadarche is that pubic hair and body odor changes by themselves do not prove that central puberty is underway for an individual child.


Hormonal changes in boys

Early stages of male hypothalamic maturation seem to be very similar to the early stages of female puberty, though occurring about 1–2 years later. LH stimulates the Leydig cells of the testes to make testosterone and blood levels begin to rise. For much of puberty, nighttime levels of testosterone are higher than daytime. Regularity of frequency and amplitude of gonadotropin pulses seems to be less necessary for progression of male than female puberty. However, a significant portion of
testosterone Testosterone is the primary sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two cl ...
in adolescent boys is converted to estradiol. Estradiol mediates the growth spurt, bone maturation, and epiphyseal closure in boys just as in girls. Estradiol also induces at least modest development of breast tissue (
gynecomastia Gynecomastia (also spelled gynaecomastia) is the abnormal non-cancerous enlargement of one or both breasts in males due to the growth of breast tissue The breast is one of two prominences located on the upper ventral Standard anatomica ...

gynecomastia
) in a large proportion of boys. Boys who develop mild
gynecomastia Gynecomastia (also spelled gynaecomastia) is the abnormal non-cancerous enlargement of one or both breasts in males due to the growth of breast tissue The breast is one of two prominences located on the upper ventral Standard anatomica ...

gynecomastia
, a swellings under
nipple The nipple is a raised region of tissue on the surface of the breast The breast is one of two prominences located on the upper region of the of s. In females, it serves as the , which produces and secretes milk to feed s. Both females ...

nipple
s, during puberty are told the effects are temporary in some male teenagers due to high levels of
estradiol Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous cycle, estrous and menstrual cycle, menstrual female reproductive cycles. Estradiol is resp ...

estradiol
. Another hormonal change in males takes place during the teenage years for most young men. At this point in a male's life the testosterone levels slowly rise, and most of the effects are mediated through the androgen receptors by way of conversion
dihydrotestosterone Dihydrotestosterone (DHT, 5α-dihydrotestosterone, 5α-DHT, androstanolone or stanolone) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell ...
in target organs (especially that of the bowels).


Hormonal changes in girls

As the amplitude of LH pulses increases, the theca cells of the ovaries begin to produce testosterone and smaller amounts of
progesterone Progesterone (P4) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell (biology), cell. Endogenous substances and processes contrast with exo ...

progesterone
. Much of the testosterone moves into nearby cells called
granulosa cell A granulosa cell or follicular cell is a somatic cell A somatic cell (from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC ...
s. Smaller increases of FSH induce an increase in the
aromatase Aromatase, also called estrogen synthetase or estrogen synthase, is an enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are calle ...
activity of these granulosa cells, which converts most of the testosterone to estradiol for secretion into the circulation. The remaining testosterone, together with adrenal androgens is responsible for the typical androgenic changes of female puberty: pubic hair, other androgenic hair as outlined above, body odor, acne. The bioactivity of testosterone is to a large degree limited by SHBG which in turn is mainly controlled by estradiol and
prolactin Prolactin (PRL), also known as lactotropin, is a protein best known for its role in enabling mammals (and birds), usually females, to lactation, produce milk. It is influential in over 300 separate processes in various vertebrates, including hu ...
levels (estradiol stimulates, prolactin decreases SHBG synthesis). Rising levels of estradiol produce the characteristic estrogenic body changes of female puberty: growth spurt, acceleration of bone maturation and closure,
breast The breast is one of two prominences located on the upper region of the of s. In females, it serves as the , which produces and secretes milk to feed s. Both females and males develop breasts from the same tissues. At , s, in conjunction ...

breast
growth, increased fat composition, growth of the uterus, increased thickness of the
endometrium The endometrium is the inner epithelial Epithelium is one of the four basic types of animal Tissue (biology), tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly pack ...

endometrium
and the vaginal mucosa, and widening of the lower pelvis. As the estradiol levels gradually rise and the other autoamplification processes occur, a point of maturation is reached when the feedback sensitivity of the hypothalamic "gonadostat" becomes positive. This attainment of positive feedback is the hallmark of female sexual maturity, as it allows the mid cycle LH surge necessary for
ovulation Ovulation is the release of egg An egg is the organic vessel containing the in which an develops until it can survive on its own, at which point the animal hatches. An egg results from of an . Most s, (excluding s), and lay eggs, alth ...

ovulation
. Growth hormone levels rise steadily throughout puberty.
IGF1 Insulin-like growth factor 1 (IGF-1), also called somatomedin C, is a hormone A hormone (from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, ...
levels rise and then decline as puberty ends. Growth finishes and adult height is attained as the estradiol levels complete closure of the
epiphyses The epiphysis is the rounded end of a long bone, at its joint A joint or articulation (or articular surface) is the connection made between bones in the body which link the skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiol ...
.


Stages

*
adrenarche Adrenarche is an early stage in sexual maturation that happens in some higher primates and in humans, typically peaks at around 20 years of age, and is eventually involved in the development of pubic hair, body odor, skin oiliness, and acne. Dur ...
(approximately age 11) * gonadarche (approximately age 8) *
thelarche Thelarche is the onset of secondary breast development, which often represents the beginning of pubertal development. The initial growth of breasts occurs during fetal development in both males and females. Thelarche is the stage at which male and ...
(approximately age 11 in females) *
pubarche Pubarche refers to the first appearance of pubic hair at puberty Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the ...
(approximately age 12) *
menarche Menarche ( ; ) is the first , or first , in female s. From both social and medical perspectives, it is often considered the central event of female , as it signals the possibility of . Girls experience menarche at different ages. Having menarc ...
(approximately age 12.5 in females) *
spermarche Spermarche—also known as semenarche—is the beginning of development of sperm Sperm is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive ...
(approximately age 13.5 in malesAge of onset of spermaturia (spermache) in 669 Mexican children and its relation to secondary sexual characteristics and height
/ref>)


Hormone levels


See also

*
Adolescent sexuality Adolescent sexuality is a stage of human development in which adolescents experience and explore sexual feelings. Interest in sexuality intensifies during the onset of puberty Puberty is the process of physical changes through which a child's ...
*
Child sexualityDevelopment of sexuality Human sexuality is the way people experience and express themselves Human sexual activity, sexually. This involves biological, erotic, Physical intimacy, physical, Emotional intimacy, emotional, social, or Spirituality, ...
*
Delayed puberty Delayed puberty is when a person lacks or has incomplete development of specific sexual characteristics Sexual characteristics are physical or behavioral traits of an organism In biology, an organism (from Ancient Greek, Greek: ὀργαν ...
*
Eunuch A eunuch ( ) is a man A man is an adult male Male (♂) is the sex of an organism that produces the gamete known as sperm. A male gamete can fuse with a larger female gamete, or ovum, in the process of fertilization. A male cannot ...

Eunuch
*
Hebephilia Hebephilia is the strong, persistent sexual interest by adults in puberty, pubescent children who are in early adolescence, typically ages 11–14 and showing Tanner stages 2 to 3 of physical development.} It differs from pedophilia (the primary or ...
*
Kallmann syndrome Kallmann syndrome (KS) is a genetic disorder that prevents a person from starting or fully completing puberty Puberty is the process of physical changes through which a child Biologically, a child (plural children) is a human Hum ...
*
Precocious puberty In medicine Medicine is the science Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity, awareness, or understanding of someone or something, such as facts ( descriptive knowledge), ...
* Puberphonia *
Secondary sex characteristic Secondary sex characteristics are features that appear during puberty Puberty is the process of physical changes through which a child Biologically, a child (plural children) is a human Humans (''Homo sapiens'') are the most populo ...
* Seclusion of girls at puberty


References


Further reading

* * * * * * Colburn, T., Dumanoski, D. and Myers, J.P. Our Stolen Future, 1996, Plume: New York. * Ducros, A. and Pasquet, P. "Evolution de l'âge d'apparition des premières règles (ménarche) en France". ''Biométrie Humaine'' (1978), 13, 35–43. * Newer data suggesting that lower age thresholds for evaluation should be used. * Plant TM, Lee PA, eds. ''The Neurobiology of Puberty''. Bristol: Society for Endocrinology, 1995. Proceedings of the latest (4th) International Conference on the Control of the Onset of Puberty, containing summaries of current theories of physiological control, as well as GnRH analog treatment. * Highly useful growth charts with integrated standards for stages of puberty. *Sizonenko, PC
Role of sex steroids during development—integration
in Bourguignon, Jean Pierre & Tony M. Plant. The Onset of Puberty in Perspective: Proceedings of the 5th International Conference on the Control of the Onset of Puberty, Held in Liège, Belgium, 26–28 September 1999. Elsevier. Amsterdam & New York 2000. . pp 299–306.


External links


Support for teens
(archive)
University of Maryland guide to puberty and adolescenceGrowing Up Sexually: A World AtlasPictures and detailed information about breast development during puberty


''ScienceDaily'', December 1, 2005 * *
Puberty in girls: interactive animation of Tanner stages

Puberty in boys: interactive animation of Tanner stages
{{Authority control Adolescence Human development Human female endocrine system Sexuality and age