Penile agenesis
Encyclopedia
Penile agenesis is a birth defect in human
s, occurring about once in 5–6 million male births, in which a male child is born without a penis
.
A partner condition is testicular or gonadal agenesis. This is when a male child is born without gonads and consequently develops no testes.
Penile agenesis occurs often as a consequence of Testicular agenesis, but the reverse is never the case.
Most patients in both cases have no known family history, and those who have an otherwise normal male anatomy.
(5aDHT) in the male body. Where the gonads fail to metamorphose into testes, there is no 5aDHT. Therefore the masculising process that builds the genital tubercle
, the precursor to the penis, is stillborn. When this happens, the child is born with both penile and testicular agenesis and is known by the slang term "nullo". This combination of both conditions is estimated to occur in between 20-30 million male births.
Penile agenesis can exist independently after full testicular development; in this case its cause is unknown.
runs down the anal wall, to be pulled away by the genital tubercle during male development. Without male development this does not occur. The urethra can be surgically redirected to the rim of the anus
immediately after birth to enable urination and avoid consequent internal irritation from urea
concentrate. In such cases, the perineum
may be left devoid of any genitalia, male or female.
A working penis transplant on to an agenetic patient has never been successful. Only one major penis graft was successfully completed. This occurred in China and the patient shortly rejected it on psychological grounds. However a full female or agenetic to male transplant is not yet facilitated to fulfil full reproductive functions.
Males with testicular agenesis tend not to produce the reproductive hormone 5aDHT at any stage of their lives. As a result, they tend toward prepubescent appearance, with infantile skin texture, developing little body hair particularly in the crotch
area, even vellus hair.Without genitalia of either sex, the perineum
is therefore left smooth. Also muscular development is retarded and testicular agenetics are of rather frail build with short limbs and small hands and feet.
However certain male features are results of other male gender-marker hormones, androgens, which develop male secondary sex characteristics, among which features are the deepening of the voice and facial hair.
, despite having a normal 46,XY male karyotype
and no female sexual characteristics. This practice was controversial, and many individuals decided to live as males again when they reached puberty or their early twenties. The New Zealand sexologist John Money
was the principle theorist who argued that boys born without an "adequate" penis, or who lost their penis in an accident, should be raised as sex reassigned girls. The book As Nature Made Him chronicles the disastrous results of the application of Money's theories in the Bruce/Brenda case. The anatomy underlying the failure of these cases is not well understood. In most males, the development of the embryo into a female is prevented by Anti-Müllerian hormones
. These hormones are commonly believed to be created in the testes, but they nevertheless still appear to be produced in male embryos lacking testes.
In summary, gender reassignment fails to take account of the male secondary sex characteristics and consequent masculine personality traits which develop independently of the reproductive system
.
Human
Humans are the only living species in the Homo genus...
s, occurring about once in 5–6 million male births, in which a male child is born without a penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
.
A partner condition is testicular or gonadal agenesis. This is when a male child is born without gonads and consequently develops no testes.
Penile agenesis occurs often as a consequence of Testicular agenesis, but the reverse is never the case.
Most patients in both cases have no known family history, and those who have an otherwise normal male anatomy.
Causes
In an embryo, the conversion of the gonads into testicles in males-to-be and into ovaries in females-to-be is the function of Leydig cells. In testicular agenesis, this process fails. Penile agenesis can be caused by testicular agenesis. Testes are the sole producer of 5-alpha dihydrotestosteroneDihydrotestosterone
Dihydrotestosterone is an androgen or male sex hormone. The enzyme 5α-reductase synthesises DHT in the prostate, testes, hair follicles, and adrenal glands...
(5aDHT) in the male body. Where the gonads fail to metamorphose into testes, there is no 5aDHT. Therefore the masculising process that builds the genital tubercle
Genital tubercle
A phallic tubercle or genital tubercle is a body of tissue present in the development of the urinary and reproductive organs. It forms in the ventral, caudal region of mammalian embryos of both sexes, and eventually develops into a phallus...
, the precursor to the penis, is stillborn. When this happens, the child is born with both penile and testicular agenesis and is known by the slang term "nullo". This combination of both conditions is estimated to occur in between 20-30 million male births.
Penile agenesis can exist independently after full testicular development; in this case its cause is unknown.
Treatment
A problem for people with penile agenesis is the absence of a urinary outlet. Before genital metamorphosis, the urethraUrethra
In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...
runs down the anal wall, to be pulled away by the genital tubercle during male development. Without male development this does not occur. The urethra can be surgically redirected to the rim of the anus
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
immediately after birth to enable urination and avoid consequent internal irritation from urea
Urea
Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....
concentrate. In such cases, the perineum
Perineum
In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...
may be left devoid of any genitalia, male or female.
A working penis transplant on to an agenetic patient has never been successful. Only one major penis graft was successfully completed. This occurred in China and the patient shortly rejected it on psychological grounds. However a full female or agenetic to male transplant is not yet facilitated to fulfil full reproductive functions.
Physical appearance
Males with penile agenesis but normal testes are of otherwise normal male appearance.Males with testicular agenesis tend not to produce the reproductive hormone 5aDHT at any stage of their lives. As a result, they tend toward prepubescent appearance, with infantile skin texture, developing little body hair particularly in the crotch
Crotch
The term crotch may be used to describe the region of an object where it splits into two or more limbs. This can include trees, animals, buildings, in wiring diagrams, etc....
area, even vellus hair.Without genitalia of either sex, the perineum
Perineum
In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...
is therefore left smooth. Also muscular development is retarded and testicular agenetics are of rather frail build with short limbs and small hands and feet.
However certain male features are results of other male gender-marker hormones, androgens, which develop male secondary sex characteristics, among which features are the deepening of the voice and facial hair.
Raising agenetics as females
People with either penile agenesis or testicular agenesis, but not both, usually continue as males throughout their lives. Historically, people with both penile and testicular agenesis were raised as females and eventually underwent sex reassignment surgerySex reassignment surgery
Sex reassignment surgery is a term for the surgical procedures by which a person's physical appearance and function of their existing sexual characteristics are altered to resemble...
, despite having a normal 46,XY male karyotype
Karyotype
A karyotype is the number and appearance of chromosomes in the nucleus of an eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism.p28...
and no female sexual characteristics. This practice was controversial, and many individuals decided to live as males again when they reached puberty or their early twenties. The New Zealand sexologist John Money
John Money
John William Money was a psychologist, sexologist and author, specializing in research into sexual identity and biology of gender...
was the principle theorist who argued that boys born without an "adequate" penis, or who lost their penis in an accident, should be raised as sex reassigned girls. The book As Nature Made Him chronicles the disastrous results of the application of Money's theories in the Bruce/Brenda case. The anatomy underlying the failure of these cases is not well understood. In most males, the development of the embryo into a female is prevented by Anti-Müllerian hormones
Anti-müllerian hormone
Anti-Müllerian hormone also known as AMH is a protein that, in humans, is encoded by the AMH gene. It inhibits the development of the Müllerian ducts in the male embryo. It has also been called Müllerian inhibiting factor , Müllerian-inhibiting hormone , and Müllerian-inhibiting substance...
. These hormones are commonly believed to be created in the testes, but they nevertheless still appear to be produced in male embryos lacking testes.
In summary, gender reassignment fails to take account of the male secondary sex characteristics and consequent masculine personality traits which develop independently of the reproductive system
Reproductive system
The reproductive system or genital system is a system of organs within an organism which work together for the purpose of reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes...
.
See also
- DiphalliaDiphalliaDiphallia, penile duplication , diphallic terata, or diphallasparatus, is a medical condition in which a male infant is born with two penises. This is an extremely rare disorder with only approximately 100 cases of diphallia recorded since the first, reported by Johannes Jacob Wecker in 1609...
, a condition in which a male is born with two penises - AphalliaAphalliaAphallia is a congenital malformity in which the phallus is absent. The word is derived from the Greek "a" for negative or no, and "phallia" for penis.-Incidence/prevalence:...
, which includes penile agenesis and also the birth of a female child without a clitorisClitorisThe 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...