In biology and medicine,
virilization refers to the biological development of sex differences, changes which make a
maleMale refers to the sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...
body different from a
femaleFemale is the sex of an organism, or a part of an organism, which produces mobile ova .- Defining Characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
body. Most of the changes of virilization are produced by
androgenAndrogen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. This includes the activity of the accessory male sex organs and...
s. Virilization is most commonly used in three medical and
biology of genderThe biology of gender is scientific analysis of the physical basis for behavioural differences between men and women. It is more specific than sexual dimorphism, which covers physical and behavioural differences between males and females of any sexually reproducing species, or sexual...
contexts: prenatal
sexual differentiationSexual differentiation is the process of development of the differences between males and females from an undifferentiated zygote...
, the postnatal changes of normal male
pubertyPuberty is the process of physical changes by which a child's body becomes an adult body capable of reproduction. Puberty is initiated by hormone signals from the brain to the gonads . In response, the gonads produce a variety of hormones that stimulate the growth, function, or transformation of...
, and excessive androgen effects in girls or women.
In the prenatal period, virilization refers to closure of the
perineumIn human anatomy, the perineum is generally defined as the surface region in both males and females between the pubic symphysis and the coccyx. The perineum is the region of the body inferior to the pelvic diaphragm and between the legs. It is a diamond-shaped area on the inferior surface of the...
, thinning and rugation of the
scrotumIn some male mammals the scrotum is a protuberance of skin and muscle containing the testicles. It is an extension of the abdomen, and is located between the penis and anus. In humans and some other mammals, the base of the scrotum becomes covered with curly pubic hairs at puberty...
, growth of the
phallusPhallus can refer to a penis, or to an object shaped like a penis. The word comes from Late Latin "phallus", from Ancient Greek "φαλλός" phallos, penis.-In art:...
, and closure of the
urethral grooveThe urethral groove is a temporary linear indentation on the underside of the male penis during embryonic development.In humans, it typically appears around 8 weeks of gestation and becomes closed into a normal male urethra by the 12th week....
to the tip of the
penisThe penis is an external sexual organ of certain biologically male organisms, in both vertebrates and invertebrates....
.
In biology and medicine,
virilization refers to the biological development of sex differences, changes which make a
maleMale refers to the sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...
body different from a
femaleFemale is the sex of an organism, or a part of an organism, which produces mobile ova .- Defining Characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
body. Most of the changes of virilization are produced by
androgenAndrogen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. This includes the activity of the accessory male sex organs and...
s. Virilization is most commonly used in three medical and
biology of genderThe biology of gender is scientific analysis of the physical basis for behavioural differences between men and women. It is more specific than sexual dimorphism, which covers physical and behavioural differences between males and females of any sexually reproducing species, or sexual...
contexts: prenatal
sexual differentiationSexual differentiation is the process of development of the differences between males and females from an undifferentiated zygote...
, the postnatal changes of normal male
pubertyPuberty is the process of physical changes by which a child's body becomes an adult body capable of reproduction. Puberty is initiated by hormone signals from the brain to the gonads . In response, the gonads produce a variety of hormones that stimulate the growth, function, or transformation of...
, and excessive androgen effects in girls or women.
Prenatal virilization
In the prenatal period, virilization refers to closure of the
perineumIn human anatomy, the perineum is generally defined as the surface region in both males and females between the pubic symphysis and the coccyx. The perineum is the region of the body inferior to the pelvic diaphragm and between the legs. It is a diamond-shaped area on the inferior surface of the...
, thinning and rugation of the
scrotumIn some male mammals the scrotum is a protuberance of skin and muscle containing the testicles. It is an extension of the abdomen, and is located between the penis and anus. In humans and some other mammals, the base of the scrotum becomes covered with curly pubic hairs at puberty...
, growth of the
phallusPhallus can refer to a penis, or to an object shaped like a penis. The word comes from Late Latin "phallus", from Ancient Greek "φαλλός" phallos, penis.-In art:...
, and closure of the
urethral grooveThe urethral groove is a temporary linear indentation on the underside of the male penis during embryonic development.In humans, it typically appears around 8 weeks of gestation and becomes closed into a normal male urethra by the 12th week....
to the tip of the
penisThe penis is an external sexual organ of certain biologically male organisms, in both vertebrates and invertebrates....
. In this context
masculinization is synonymous with virilization. Prenatal virilization of genetic females and undervirilization of genetic males are common causes of ambiguous genitalia and intersex conditions.
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 can be produced or the body is completely insensitive to it, and results 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 with
hypospadiasHypospadias is a birth defect of the urethra in the male that involves an abnormally placed urinary meatus . Instead of opening at the tip of the glans of the penis, a hypospadic urethra opens anywhere along a line running from the tip along the underside of the shaft to the junction of the penis...
. Examples of undervirilization are
androgen insensitivity syndromeAndrogen insensitivity syndrome , also referred to as androgen resistance syndrome, is a set of disorders of sex development caused by mutations of the gene encoding the androgen receptor. The nature of the resulting problem varies according to the structure and sensitivity of the abnormal receptor...
, 5 alpha reductase deficiency, and some forms of
congenital adrenal hyperplasiaCongenital adrenal hyperplasia refers to any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the biochemical steps of production of cortisol from cholesterol by the adrenal glands ....
.
Prenatal virilization (or masculinization) of a genetically female fetus can occur when an excessive amount of androgen is produced by the fetal
adrenal glandIn mammals, the adrenal glands are the star-shaped endocrine glands that sit on top of the kidneys; their name indicates that position...
s or is present in maternal blood. In the severest form of
congenital adrenal hyperplasiaCongenital adrenal hyperplasia refers to any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the biochemical steps of production of cortisol from cholesterol by the adrenal glands ....
complete masculinization of a genetically female fetus results in an apparently normal baby boy with no palpable testes. More often, the virilization is partial and the genitalia are ambiguous.
Normal virilization
In common as well as medical usage, virilization often refers to the process of normal male
pubertyPuberty is the process of physical changes by which a child's body becomes an adult body capable of reproduction. Puberty is initiated by hormone signals from the brain to the gonads . In response, the gonads produce a variety of hormones that stimulate the growth, function, or transformation of...
, in which
testosteroneTestosterone is a steroid hormone from the androgen group. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands. It is the principal male sex hormone and an anabolic steroid.In men,...
changes a boy's body into a man's. These effects include growth of the penis and testes, accelerated growth, development of
pubic hairPubic hair is hair in the frontal genital area, the crotch, and sometimes at the top of the inside of the legs; these areas form the pubic region....
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 either boys or girls due to excessive amounts of androgens. Typical effects of virilization in children are
pubic hairPubic hair is hair in the frontal genital area, the crotch, and sometimes at the top of the inside of the legs; these areas form the pubic region....
, accelerated growth and bone maturation, increased muscle strength,
acneAcne vulgaris is a common skin condition, caused by changes in pilosebaceous units, skin structures consisting of a hair follicle and its associated sebaceous gland, via androgen stimulation. It is characterized by noninflammatory follicular papules or comedones and by inflammatory papules,...
, adult body odor, and sometimes growth of the penis. In a boy, virilization may signal
precocious pubertyPrecocious puberty is an unusually early onset of puberty, the process of sexual maturation triggered by the brain or exogenous chemicals, which usually begins in late childhood and results in reproductive maturity and completion of growth...
, while
congenital adrenal hyperplasiaCongenital adrenal hyperplasia refers to any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the biochemical steps of production of cortisol from cholesterol by the adrenal glands ....
and androgen producing tumors (usually) of the
gonadThe gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...
s or adrenals are occasional causes in both sexes.
Virilization in adolescent or adult women
Virilization in a woman can manifest as
clitoralThe clitoris is a sexual organ that is present only in female mammals. In humans, the visible button-like portion is located near the anterior junction of the labia minora, above the opening of the urethra and vagina. Unlike the penis, which is homologous to the clitoris, the clitoris does not...
enlargement, increased muscle strength, acne,
hirsutismHirsutism is excessive and increased hair growth on female humans in locations where the occurrence of terminal hair normally is minimal or absent. For example, a beard, or chest hair. It refers to a male pattern of body hair and it is therefore primarily of cosmetic and psychological concern...
, frontal hair thinning, deepening of the voice, and menstrual disruption due to
anovulationAn anovulatory cycle is a cycle during which the ovaries fail to release an oocyte. Therefore, ovulation does not take place. However, a woman who does not ovulate at each menstrual cycle is not necessarily going through menopause...
.
Some of the possible causes of virilization in women are:
- Polycystic ovary syndrome
Polycystic ovary syndrome is an endocrine disorder that affects approximately 5% of all women.It occurs amongst all races and nationalities, is the most common hormonal disorder among women of reproductive age, and is a leading cause of infertility.The principal features are obesity, anovulation ,...
- Androgen
Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. This includes the activity of the accessory male sex organs and...
-producing tumors of the
- ovaries
- adrenal glands
- pituitary gland
- Hypothyroidism
Hypothyroidism is the disease state in humans and in animals caused by insufficient production of thyroid hormone by the thyroid gland. Cretinism is a form of hypothyroidism found in infants.-Causes:...
- Anabolic steroid
Anabolic steroids, or anabolic-androgenic steroids , are a class of steroid hormones related to the hormone testosterone. They increase protein synthesis within cells, which results in the buildup of cellular tissue , especially in muscles...
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, and "CAH" in most contexts refers to 21-hydroxylase deficiency...
(late-onset)
- Hormone replacement therapy (female-to-male)
Hormone replacement therapy for transgender people replaces the hormones naturally occurring in their bodies with those of the other sex. However, not all cases of hormone replacement therapy are used by transgender people. Some reasons for this include men who wish to have a hair-free body, as a...
See also
- Sexual differentiation
Sexual differentiation is the process of development of the differences between males and females from an undifferentiated zygote...
- Secondary sex characteristic
Secondary sex characteristics are traits that distinguish the two sexes of a species, but that are not directly part of the reproductive system. They are believed to be the product of sexual selection for traits which give an individual an advantage over its rivals in courtship and aggressive...
s
- Ambiguous genitalia
- Androgen
Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. This includes the activity of the accessory male sex organs and...
- Clitoromegaly
Clitoromegaly is an abnormal enlargement of the clitoris ....
- Hirsutism
Hirsutism is excessive and increased hair growth on female humans in locations where the occurrence of terminal hair normally is minimal or absent. For example, a beard, or chest hair. It refers to a male pattern of body hair and it is therefore primarily of cosmetic and psychological concern...