Micropenis
Encyclopedia
Micropenis is an unusually small penis
. A common criterion is a dorsal (measured on top) erect penile length
of at least 2.5 standard deviation
s smaller than the mean
human penis size
. The condition is usually recognized shortly after birth
. The term is most often used medically when the rest of the penis, scrotum
, and perineum
are without ambiguity, such as hypospadias
.
Of the abnormal conditions associated with micropenis, most are conditions of reduced prenatal androgen
production or effect, such as abnormal testicular development (testicular dysgenesis, Klinefelter syndrome, Leydig cell hypoplasia), specific defects of testosterone
or dihydrotestosterone synthesis (17,20-lyase deficiency, 5α-reductase deficiency
), androgen insensitivity syndrome
s, inadequate pituitary stimulation (gonadotropin
deficiency), and other forms of congenital hypogonadism
. Micropenis can also occur as part of many genetic malformation syndromes that do not involve the sex chromosomes. It is sometimes a sign of congenital growth-hormone deficiency
or congenital hypopituitarism
. Several homeobox
genes affect penis and digit size without detectable hormone abnormalities.
After evaluation to detect any of the conditions described above, micropenis can often be treated in infancy with injections of various hormone
s, such as human chorionic gonadotropin
and testosterone
.
Most eight- to fourteen-year-old boys referred for micropenis do not have the micropenis condition. Such concerns are usually explained by one of the following:
Growth of the penis both before birth and during childhood and puberty is strongly influenced by testosterone
and, to a lesser degree, growth hormone
; but their value in the treatment of micropenis is mainly limited to conditions of hormone deficiency, such as hypopituitarism
or hypogonadism
.
Regardless of the cause of micropenis, if it is recognized in infancy, a brief course of testosterone is often prescribed (usually no more than 3 months). This usually induces a small amount of growth, confirming the likelihood of further growth at puberty, but rarely achieves normal size. No additional testosterone is given during childhood, to avoid unwanted virilization
and bone maturation. (There also is some evidence that premature administration of testosterone can lead to reduced penis size in the adult.)
Testosterone treatment is resumed in adolescence only for boys with hypogonadism. Penile growth is completed at the end of puberty, similarly to the completion of height growth
, and provision of extra testosterone to post-pubertal adults produces little or no further growth.
for penis enlargement
have been devised and performed; but they are not generally considered successful enough to be widely adopted and are rarely performed in childhood.
In extreme cases of micropenis, there is barely any shaft, and the glans appears to sit almost on the pubic skin. From the 1960s until the late 1970s, it was common for sex reassignment
and surgery
to be recommended. This was especially likely if evidence suggested that response to additional testosterone and pubertal testosterone would be poor. If parents accepted, the boy would be reassigned and renamed as a girl, and surgery performed to remove the testes and construct an artificial vagina
. This was based on three now questioned assumptions:
Johns Hopkins Hospital
, the center most known for this approach, performed twelve such reassignments from 1960 to 1980, most notably that of David Reimer
(whose penis was destroyed by a circumcision accident), overseen by Dr. John Money
. By the mid 1990s, reassignment was less often offered, and all three premises had been challenged. Former subjects of such surgery, vocal about their dissatisfaction with adult outcome, played a large part in discouraging this practice. Sexual reassignment is rarely performed today for severe micropenis (although the question of raising the boy as a girl is sometimes still discussed.) Much inaccurate or exaggerated folklore on this topic is available on the internet. (See "History of intersex surgery
" for a fuller discussion.)
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
. A common criterion is a dorsal (measured on top) erect penile length
Human penis size
Human penis size is the measured length and width of the human penis. The most accurate measurement of the human penis comes from several measurements at different times, as there is natural variability in size due to arousal level, time of day, room temperature, frequency of sexual activity, and...
of at least 2.5 standard deviation
Standard deviation
Standard deviation is a widely used measure of variability or diversity used in statistics and probability theory. It shows how much variation or "dispersion" there is from the average...
s smaller than the mean
Mean
In statistics, mean has two related meanings:* the arithmetic mean .* the expected value of a random variable, which is also called the population mean....
human penis size
Human penis size
Human penis size is the measured length and width of the human penis. The most accurate measurement of the human penis comes from several measurements at different times, as there is natural variability in size due to arousal level, time of day, room temperature, frequency of sexual activity, and...
. The condition is usually recognized shortly after birth
Childbirth
Childbirth is the culmination of a human pregnancy or gestation period with the birth of one or more newborn infants from a woman's uterus...
. The term is most often used medically when the rest of the penis, scrotum
Scrotum
In some male mammals the scrotum is a dual-chambered protuberance of skin and muscle containing the testicles and divided by a septum. It is an extension of the perineum, and is located between the penis and anus. In humans and some other mammals, the base of the scrotum becomes covered with curly...
, and perineum
Perineum
In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...
are without ambiguity, such as hypospadias
Hypospadias
Hypospadias is a birth defect of the urethra in the male that involves an abnormally placed urinary meatus...
.
Causes
Androgen
Androgen, also called androgenic hormone or testoid, is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of male characteristics in vertebrates by binding to androgen receptors...
production or effect, such as abnormal testicular development (testicular dysgenesis, Klinefelter syndrome, Leydig cell hypoplasia), specific defects of testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. 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...
or dihydrotestosterone synthesis (17,20-lyase deficiency, 5α-reductase deficiency
5-alpha-reductase deficiency
5-Alpha-reductase deficiency is an autosomal recessive intersex condition caused by a mutation of the 5-alpha reductase type 2 gene.-Normal function:...
), androgen insensitivity syndrome
Androgen insensitivity syndrome
Androgen insensitivity syndrome is a condition that results in the partial or complete inability of the cell to respond to androgens. The unresponsiveness of the cell to the presence of androgenic hormones can impair or prevent the masculinization of male genitalia in the developing fetus, as...
s, inadequate pituitary stimulation (gonadotropin
Gonadotropin
Gonadotropins are protein hormones secreted by gonadotrope cells of the pituitary gland of vertebrates. This is a family of proteins, which include the mammalian hormones follitropin , lutropin , placental chorionic gonadotropins hCG and eCG and chorionic gonadotropin , as well as at least two...
deficiency), and other forms of congenital hypogonadism
Hypogonadism
Hypogonadism is a medical term for decreased functional activity of the gonads. Low testosterone is caused by a decline or deficiency in gonadal production of testosterone in males...
. Micropenis can also occur as part of many genetic malformation syndromes that do not involve the sex chromosomes. It is sometimes a sign of congenital growth-hormone deficiency
Growth hormone deficiency
Growth hormone deficiency is a medical condition in which the body does not produce enough growth hormone . Growth hormone, also called somatotropin, is a polypeptide hormone which stimulates growth and cell reproduction...
or congenital hypopituitarism
Hypopituitarism
Hypopituitarism is the decreased secretion of one or more of the eight hormones normally produced by the pituitary gland at the base of the brain...
. Several homeobox
Homeobox
A homeobox is a DNA sequence found within genes that are involved in the regulation of patterns of anatomical development in animals, fungi and plants.- Discovery :...
genes affect penis and digit size without detectable hormone abnormalities.
After evaluation to detect any of the conditions described above, micropenis can often be treated in infancy with injections of various hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
s, such as human chorionic gonadotropin
Human chorionic gonadotropin
Human chorionic gonadotropin or human chorionic gonadotrophin is a glycoprotein hormone produced during pregnancy that is made by the developing embryo after conception and later by the syncytiotrophoblast .. Some tumors make this hormone; measured elevated levels when the patient is not...
and testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. 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...
.
Most eight- to fourteen-year-old boys referred for micropenis do not have the micropenis condition. Such concerns are usually explained by one of the following:
- a penis concealed in suprapubic fat (extra fat around the mons pubis).
- a large body and frame for which a prepubertal penis simply appears too small.
- delayed pubertyDelayed pubertyPuberty is described as delayed puberty with exceptions when an organism has passed the usual age of onset of puberty with no physical or hormonal signs that it is beginning. Puberty may be delayed for several years and still occur normally, in which case it is considered constitutional delay, a...
with every reason to expect good future growth.
Hormone treatment
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. 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...
and, to a lesser degree, growth hormone
Growth hormone
Growth hormone is a peptide hormone that stimulates growth, cell reproduction and regeneration in humans and other animals. Growth hormone is a 191-amino acid, single-chain polypeptide that is synthesized, stored, and secreted by the somatotroph cells within the lateral wings of the anterior...
; but their value in the treatment of micropenis is mainly limited to conditions of hormone deficiency, such as hypopituitarism
Hypopituitarism
Hypopituitarism is the decreased secretion of one or more of the eight hormones normally produced by the pituitary gland at the base of the brain...
or hypogonadism
Hypogonadism
Hypogonadism is a medical term for decreased functional activity of the gonads. Low testosterone is caused by a decline or deficiency in gonadal production of testosterone in males...
.
Regardless of the cause of micropenis, if it is recognized in infancy, a brief course of testosterone is often prescribed (usually no more than 3 months). This usually induces a small amount of growth, confirming the likelihood of further growth at puberty, but rarely achieves normal size. No additional testosterone is given during childhood, to avoid unwanted virilization
Virilization
In biology and medicine, virilization refers to the biological development of sex differences, changes that make a male body different from a female body. Most of the changes of virilization are produced by androgens...
and bone maturation. (There also is some evidence that premature administration of testosterone can lead to reduced penis size in the adult.)
Testosterone treatment is resumed in adolescence only for boys with hypogonadism. Penile growth is completed at the end of puberty, similarly to the completion of height growth
Human height
Human height is the distance from the bottom of the feet to the top of the head in a human body standing erect.When populations share genetic background and environmental factors, average height is frequently characteristic within the group...
, and provision of extra testosterone to post-pubertal adults produces little or no further growth.
Surgery
Because hormone treatment rarely achieves average size, several surgical techniques similar to phalloplastyPhalloplasty
Phalloplasty refers to the construction of a penis or, sometimes, artificial modification of the penis by surgery, often for cosmetic purposes. It is also occasionally used to refer to penis enlargement....
for penis enlargement
Penis enlargement
Penis enlargement procedures are techniques alleged to make the human penis increase in girth, length, or hardness. Often, in the course of advertising fraudulent products, the distinction between temporary enlargement, i.e...
have been devised and performed; but they are not generally considered successful enough to be widely adopted and are rarely performed in childhood.
In extreme cases of micropenis, there is barely any shaft, and the glans appears to sit almost on the pubic skin. From the 1960s until the late 1970s, it was common for sex reassignment
Sex reassignment
Sex reassignment may refer to:* Sex reassignment, changing the sex assignment of an infant or child by parents and doctors, usually because of fuller understanding of an intersex condition....
and surgery
History of intersex surgery
The history of intersex surgery is intertwined with the development of the specialities of pediatric surgery, pediatric urology, and pediatric endocrinology, with our increasingly refined understanding of sexual differentiation, with the development of political advocacy groups united by a sexual...
to be recommended. This was especially likely if evidence suggested that response to additional testosterone and pubertal testosterone would be poor. If parents accepted, the boy would be reassigned and renamed as a girl, and surgery performed to remove the testes and construct an artificial vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
. This was based on three now questioned assumptions:
- gender identity and sex differences were solely a matter of social learning rather than biology.
- a male with a penis too small to put into a vagina could not find a satisfactory social and sexual place in society.
- a functionally acceptable vagina could be constructed surgically.
Johns Hopkins Hospital
Johns Hopkins Hospital
The Johns Hopkins Hospital is the teaching hospital and biomedical research facility of Johns Hopkins University School of Medicine, located in Baltimore, Maryland . It was founded using money from a bequest by philanthropist Johns Hopkins...
, the center most known for this approach, performed twelve such reassignments from 1960 to 1980, most notably that of David Reimer
David Reimer
David Reimer was a Canadian man who was born as a healthy male, but was sexually reassigned and raised as female after his penis was accidentally destroyed during circumcision. Psychologist John Money oversaw the case and reported the reassignment as successful, and as evidence that gender...
(whose penis was destroyed by a circumcision accident), overseen by Dr. John Money
John Money
John William Money was a psychologist, sexologist and author, specializing in research into sexual identity and biology of gender...
. By the mid 1990s, reassignment was less often offered, and all three premises had been challenged. Former subjects of such surgery, vocal about their dissatisfaction with adult outcome, played a large part in discouraging this practice. Sexual reassignment is rarely performed today for severe micropenis (although the question of raising the boy as a girl is sometimes still discussed.) Much inaccurate or exaggerated folklore on this topic is available on the internet. (See "History of intersex surgery
History of intersex surgery
The history of intersex surgery is intertwined with the development of the specialities of pediatric surgery, pediatric urology, and pediatric endocrinology, with our increasingly refined understanding of sexual differentiation, with the development of political advocacy groups united by a sexual...
" for a fuller discussion.)
External links
- Into the Hands of Babes, by Melissa Hendricks, Johns Hopkins Magazine
- Gender Self Reassignment in an XY Adolescent Female with Ambiguous Genitalia, from PediatricsPediatrics (journal)Pediatrics is an official peer-reviewed journal of the American Academy of Pediatrics. In the inaugural January 1948 issue, the journal's first editor, Hugh McCulloch, articulated the journal's vision: "The content of the journal is... intended to encompass the needs of the whole child in his...
(PDF) - Effect of penile size on nocturnal erections: evaluation with NPTR testing with men having micropenis from the International Journal of Impotence Research