Thelarche
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Thelarche, also known as breast budding, is the onset of secondary breast development, often representing the beginning of pubertal development. It is the stage at which male and female breasts differentiate due to variance in hormone levels; however, some males have a condition in which they develop breasts, 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 as a result of a hormone imbalance between estrogens and androgens. Updated by Brent Wisse (1 ...
. Thelarche typically occurs between the ages of 8 and 13 years with significant variation between individuals. However, the initial growth of breast tissue occurs during fetal development regardless of sex. Usually, females experience menarche about two years after thelarche has begun, with complete breast development from thelarche to adult breasts, taking between 2 and 4 years. Moreover,
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 brain to the gonads: the ovaries in a girl, the testes in a boy. ...
is considered delayed if breast development does not start before age 13 or if a female has not had her first period (
menarche Menarche ( ; ) is the first menstrual cycle, or first menstrual bleeding, in female humans. From both social and medical perspectives, it is often considered the central event of female puberty, as it signals the possibility of fertility. Gir ...
) within three years of thelarche. Additionally, secondary breast development occurring before the age of 7 or 8 years could be a sign of premature thelarche or
precocious puberty In medicine, precocious puberty is puberty occurring at an unusually early age. In most cases, the process is normal in every aspect except the unusually early age and simply represents a variation of normal development. In a minority of childr ...
. Of note, for some girls, thelarche will occur, with subsequent regression of breast development, and then months or years later, normal breast growth will commence again accompanied by normal pubertal changes; this is termed transient thelarche. Pubertal changes, including breast development, are assessed using the
Tanner Scale The Tanner scale (also known as the Tanner stages or Sexual Maturity Rating (SMR)) is a scale of physical development in children, adolescents and adults. The scale defines physical measurements of development based on external primary and seco ...
(Sexual Maturity Rating Scale) where stage 1 represents the lack of breast development, stage 2 is the breast budding or thelarche stage, stages 3 and 4 are continual breast growth and
areola The human areola (''areola mammae'', or ) is the pigmented area on the breast around the nipple. Areola, more generally, is a small circular area on the body with a different histology from the surrounding tissue, or other small circular ar ...
r development, and stage 5 signifies completion of development. This system does not use breast size but instead examines the shape of breasts, nipples, and areolae to determine the progression of growth. Various hormones interact and result in the changes seen during thelarche. The growth and accumulation of
adipose tissue Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular e ...
in the breasts are induced by
estrogen Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal acti ...
, while the development of
mammary gland A mammary gland is an exocrine gland in humans and other mammals that produces milk to feed young offspring. Mammals get their name from the Latin word ''mamma'', "breast". The mammary glands are arranged in organs such as the breasts in primat ...
s and areolae are caused by
progesterone Progesterone (P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the m ...
; both estrogen and progesterone are produced by
ovaries The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...
. Due to change in hormone levels, young breasts are likely to develop asymmetrically, and in many cases, adult breasts will remain unequal in size or shape.


Epidemiology and Trends

The age of thelarche has been decreasing in the past few decades. Between 1973 and 2013, the age of thelarche decreased at a rate of 0.24 years per decade. Other contemporary trends that may be contributing to this change in the onset of thelarche include increasing BMI, changes in pubertal timing, and environmental exposures. Studies also indicate associations between the average age of thelarche and race. The average age of thelarche for African American females in the United States is between 8.9 and 9.5 years, the average for Caucasians is 10-10.4 years, and the average age of thelarche for Hispanic females is approximately 9.8 years. Additionally, in African American and Mexican American girls, breast development may occur earlier than in other ethnic cohorts and can be normal in the 7th year of age. Due to the decreasing age of thelarche over time, there is discussion of adjusting the cutoff for early thelarche to 7 years old for white females and six years old for black females. Furthermore, there have been associations between obesity, chemical contaminants, and the earlier average age of thelarche. Studies have shown that obesity is associated with an earlier average age of thelarche. Moreover, the prevalence of premature thelarche has been increasing over the past several years which many attribute to pesticides. Experimental data indicate the impact of chemical contaminants in gestation and puberty, with the chemical such as phthalates having a high association with premature thelarche frequency.


Premature thelarche

Premature thelarche is a benign condition in which a young female has breast development before age eight without any accompanied pubertal changes. Individuals undergoing isolated premature thelarche do not experience
menstruation Menstruation (also known as a period, among other colloquial terms) is the regular discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina. The menstrual cycle is characterized by the rise and fall of hor ...
, pubic hair growth (
pubarche Pubarche refers to the first appearance of pubic hair at puberty. Pubarche is one of the physical changes of puberty and can occur independently of complete puberty. Pubarche usually results from rising levels of androgen and not estrogens in femal ...
), or the bone growth characteristic of puberty. Initial breast development can be bilateral or unilateral and usually begins with a firm, disc-like area of tissue under the areola, which can be mistaken for a mass but is almost always a normal physiologic process. The breast is often tender, and palpation is sometimes painful, but breast discharge is absent. Usually, the breasts do not develop past stage 3 on the Tanner Scale, hence maintaining adolescent nipples. Moreover, in 90% of patients with isolated premature thelarche, breast enlargement will resolve six months to 6 years after diagnosis. The most common age for females to develop isolated premature thelarche is between 0 and 2 years, with a prevalence rate between 2.2 and 4.7 percent of all female infants. The breasts of these females typically exhibit alternating progression and regression patterns of growth in 6-week intervals, often completely decreasing in size within 1.5 years. Due to the benign nature of the condition and the tendency to self-resolve, premature thelarche does not require treatment. However, premature thelarche should be evaluated to rule out additional causes, such as hypothyroidism or precocious puberty, especially if other symptoms are present. Such evaluations will typically involve serial examinations and radiographs.


Precocious puberty

Precocious puberty In medicine, precocious puberty is puberty occurring at an unusually early age. In most cases, the process is normal in every aspect except the unusually early age and simply represents a variation of normal development. In a minority of childr ...
is a condition where children undergo puberty before seven or eight years. Precocious puberty differs from premature thelarche in that the individual experiences additional aspects of puberty, including
menarche Menarche ( ; ) is the first menstrual cycle, or first menstrual bleeding, in female humans. From both social and medical perspectives, it is often considered the central event of female puberty, as it signals the possibility of fertility. Gir ...
,
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 involved in the development of pubic hair, body odor, skin oiliness, axillary hair, sexual ...
,
pubarche Pubarche refers to the first appearance of pubic hair at puberty. Pubarche is one of the physical changes of puberty and can occur independently of complete puberty. Pubarche usually results from rising levels of androgen and not estrogens in femal ...
,
vaginal discharge Vaginal discharge is a mixture of liquid, cells, and bacteria that lubricate and protect the vagina. This mixture is constantly produced by the cells of the vagina and cervix, and it exits the body through the vaginal opening. The composition, amou ...
, and bone growth, while the sole presence of early thelarche identifies premature thelarche. Though premature thelarche and precocious puberty are distinct conditions, there is some overlap; an estimated 14 to 18 percent of females who exhibit premature thelarche will additionally develop precocious puberty. Precocious puberty can be identified using a pelvic ultrasound to assess the size of ovaries and uterus relative to the individual's age. Other methods of diagnosis consist of blood tests to determine hormone levels and simple physician assessments with follow-up appointments to track the progression of development.


Thelarche variant

The Thelarche variant, also named exaggerated thelarche, is an intermediate condition between premature thelarche and precocious puberty. This condition resembles premature thelarche without the cyclic waxing and waning of breast growth. Pubic hair growth (
pubarche Pubarche refers to the first appearance of pubic hair at puberty. Pubarche is one of the physical changes of puberty and can occur independently of complete puberty. Pubarche usually results from rising levels of androgen and not estrogens in femal ...
) and advanced bone growth are often present in the thelarche variant. Yet, this growth does not result in complete sexual maturity as occurs with precocious puberty.


See also

*
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 involved in the development of pubic hair, body odor, skin oiliness, axillary hair, sexual ...
* Gonadarche *
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 as a result of a hormone imbalance between estrogens and androgens. Updated by Brent Wisse (1 ...
*
Menarche Menarche ( ; ) is the first menstrual cycle, or first menstrual bleeding, in female humans. From both social and medical perspectives, it is often considered the central event of female puberty, as it signals the possibility of fertility. Gir ...
*
Pubarche Pubarche refers to the first appearance of pubic hair at puberty. Pubarche is one of the physical changes of puberty and can occur independently of complete puberty. Pubarche usually results from rising levels of androgen and not estrogens in femal ...


References

{{Reproductive physiology Gynaecology Animal developmental biology Pediatrics Sexuality and age Endocrinology Developmental stages