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

androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This in ...

s. Virilization is most commonly used in three medical and biology of sex contexts: prenatal biological sexual differentiation, the postnatal changes of typical chromosomal male (46, XY)

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 bo ...

, and excessive androgen effects in typical chromosomal females (46, XX). It is also the intended result of androgen replacement therapy in males with

delayed puberty Delayed puberty is when a person lacks or has incomplete development of specific sexual characteristics past the usual age of onset of puberty. The person may have no physical or hormonal signs that puberty has begun. In the United States, girls ...

and low testosterone.

Prenatal virilization

In the prenatal period, virilization refers to closure of the

perineum The perineum in humans is the space between the anus and scrotum in the male, or between the anus and the vulva in the female. The perineum is the region of the body between the pubic symphysis (pubic arch) and the coccyx (tail bone), includi ...

, thinning and wrinkling (rugation) of the

scrotum The scrotum or scrotal sac is an anatomical male reproductive structure located at the base of the penis that consists of a suspended dual-chambered sac of skin and smooth muscle. It is present in most terrestrial male mammals. The scrotum co ...

, growth of the penis, and closure of the urethral groove to the tip 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. Such organs occur in many animals, both vertebrate and invertebrate, but males d ...

. In this context, ''masculinization'' is synonymous with ''virilization.'' Prenatal virilization of genetic females and undervirilization of genetic males are common causes of

ambiguous genitalia Intersex people are individuals born with any of several sex characteristics including chromosome patterns, gonads, or genitals that, according to the Office of the United Nations High Commissioner for Human Rights, "do not fit typical bin ...

and

intersex Intersex people are individuals born with any of several sex characteristics including chromosome patterns, gonads, or genitals that, according to the Office of the United Nations High Commissioner for Human Rights, "do not fit typical bin ...

conditions.

High

Prenatal virilization of a genetically female fetus can occur when an excessive amount of androgen is produced by the fetal

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 cortex whic ...

s or is present in maternal blood. In the severest form of

congenital adrenal hyperplasia Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders characterized by impaired cortisol synthesis. It results from the deficiency of one of the five enzymes required for the synthesis of cortisol in the adrenal cort ...

, complete masculinization of a genetically female fetus results in an apparently normal male anatomy with no palpable

testes A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testoste ...

. More often, the virilization is partial and the genitalia are ambiguous. It can also be associated with

progestin-induced virilisation Maternal use of androgens or high doses of certain weakly androgenic synthetic progestogens ( progestins) structurally related to testosterone can masculinize (virilize) the external genitalia of a female fetus during susceptible times in pregn ...

Low

''Undervirilization'' can occur if a genetic male cannot produce enough androgen or the body tissues cannot respond to it. Extreme undervirilization occurs when no significant androgen hormones can be produced or the body is completely insensitive to androgens. Both result in a female body. Partial undervirilization produces ambiguous genitalia part-way between male and female. The mildest degree of undervirilization may be a slightly small penis. Examples of undervirilization are

androgen insensitivity syndrome Androgen insensitivity syndrome (AIS) is a difference in sex development involving hormonal resistance due to androgen receptor dysfunction. It affects 1 in 20,000 to 64,000 XY ( karyotypically male) births. The condition results in the partial ...

5 alpha reductase deficiency 5 (five) is a number, numeral and digit. It is the natural number, and cardinal number, following 4 and preceding 6, and is a prime number. It has attained significance throughout history in part because typical humans have five digits on eac ...

, and some forms of

Normal virilization

In common as well as medical usage, virilization often refers to the process of normal male

. These effects include growth of the penis and testes, accelerated growth, development of pubic hair, and other androgenic hair of face, torso, and limbs, deepening of the voice, increased musculature, thickening of the jaw, prominence of the neck cartilage, and broadening of the shoulders.

Abnormal childhood virilization

Virilization can occur in childhood in both males and females due to excessive amounts of androgens. Typical effects of virilization in children are pubic hair, accelerated growth and bone maturation, increased

muscle strength Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other ...

acne Acne, also known as ''acne vulgaris'', is a long-term skin condition that occurs when dead skin cells and oil from the skin clog hair follicles. Typical features of the condition include blackheads or whiteheads, pimples, oily skin, and ...

, and adult body odor. In males, virilization may signal

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 ...

, while

and androgen producing tumors (usually) of the gonads or adrenals are occasional causes in both sexes.

In adolescent or adult females

Virilization in females can manifest as

clitoral The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of other animals. In humans, the visible portion – the glans – is at the front junction of the labia minora (inner lips), above the open ...

enlargement, increased muscle strength, acne,

hirsutism Hirsutism is excessive body hair on parts of the body where hair is normally absent or minimal. The word is from early 17th century: from Latin ''hirsutus'' meaning "hairy". It usually refers to a "male" pattern of hair growth in a female that ...

, frontal hair thinning, deepening of the voice,

menstrual The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that make pregnancy possible. The ovarian cycle controls the production and release of eggs a ...

disruption due to

anovulation Anovulation is when the ovaries do not release an oocyte during a menstrual cycle. Therefore, ovulation does not take place. However, a woman who does not ovulate at each menstrual cycle is not necessarily going through menopause. Chronic anovula ...

, and a strengthened libido. Some of the possible causes of virilization in females are: *

Androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This in ...

-producing tumors of the **

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 ...

s (see

adrenal tumor An adrenal tumor or adrenal mass is any benign or malignant neoplasms of the adrenal gland, several of which are notable for their tendency to overproduce endocrine hormones. Adrenal cancer is the presence of malignant adrenal tumors, and include ...

) **

pituitary gland In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland, about the size of a chickpea and weighing, on average, in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain. The ...

(see

pituitary adenoma Pituitary adenomas are tumors that occur in the pituitary gland. Most pituitary tumors are benign, approximately 35% are invasive and just 0.1% to 0.2% are carcinomas.Hyperthecosis * Hypothyroidism * Anabolic steroid exposure *

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency Congenital adrenal hyperplasia due to 21-hydroxylase deficiency, in all its forms, accounts for over 95% of diagnosed cases of congenital adrenal hyperplasia (CAH), and CAH in most contexts refers to 21-hydroxylase deficiency and different mutat ...

(late-onset) *

Conn's syndrome Primary aldosteronism (PA)'','' also known as primary hyperaldosteronism or Conn's syndrome, refers to the excess production of the hormone aldosterone from the adrenal glands, resulting in low renin levels and high blood pressure. This abnormalit ...

Medically induced virilization in transgender people

Transgender people who were medically assigned female at birth sometimes elect to take

hormone replacement therapy Hormone replacement therapy (HRT), also known as menopausal hormone therapy or postmenopausal hormone therapy, is a form of hormone therapy used to treat symptoms associated with female menopause. These symptoms can include hot flashes, vaginal ...

. This process causes virilization by inducing many of the effects of a typically male puberty. Many of these effects are permanent, but some effects can be reversed if the transgender individual stops or pauses their medical treatment.

Permanent virilization effects

* Deepening of the voice * Growth of facial and body hair * Male-pattern baldness * Enlargement of the clitoris *

Breast atrophy Breast atrophy is the normal or spontaneous atrophy or shrinkage of the breasts. Breast atrophy commonly occurs in women during menopause when estrogen levels decrease. It can also be caused by hypoestrogenism and/or hyperandrogenism in women i ...

– possible shrinking and/or softening of breasts

Reversible virilization effects

* Further muscle development (especially upper body) * Increased sweat and changes in body odor * Prominence of veins and coarser skin * Alterations in blood lipids (

cholesterol Cholesterol is any of a class of certain organic molecules called lipids. It is a sterol (or modified steroid), a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell mem ...

and

triglycerides A triglyceride (TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids (from ''tri-'' and ''glyceride''). Triglycerides are the main constituents of body fat in humans and other vertebrates, as we ...

) * Increased red blood cell count

Demasculinization

Demasculinization refers to the reversal of virilization. Some but not all aspects of virilization are reversible. Demasculinization occurs naturally with andropause, pathologically with

hypogonadism Hypogonadism means diminished functional activity of the gonads—the testes or the ovaries—that may result in diminished production of sex hormones. Low androgen (e.g., testosterone) levels are referred to as hypoandrogenism and low estroge ...

, and artificially or medically with

antiandrogen Antiandrogens, also known as androgen antagonists or testosterone blockers, are a class of drugs that prevent androgens like testosterone and dihydrotestosterone (DHT) from mediating their biological effects in the body. They act by blocking the ...

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 ac ...

s, and

orchiectomy Orchiectomy (also named orchidectomy, and sometimes shortened as orchi or orchie) is a surgical procedure in which one or both testicles are removed. The surgery is performed as treatment for testicular cancer, as part of surgery for transgend ...

. It is desired by

transgender women A trans woman or a transgender woman is a woman who was assigned male at birth. Trans women have a female gender identity, may experience gender dysphoria, and may transition; this process commonly includes hormone replacement therapy and ...

who have undergone the changes of pubertal masculinization, to restore and induce feminine physical traits that would otherwise be masked or never occur. Some virilized traits remain though (such as body hair, a hard

jaw The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth and serv ...

line and an enlarged larynx), due to the fashion in which virilization affects a body's physiology.

References

External links

{{Reproductive physiology Sexual dimorphism Metabolism Physiology Testosterone