Anogenital distance (AGD) is the distance from the midpoint of the

anus In mammals, invertebrates and most fish, the anus (: anuses or ani; from Latin, 'ring' or 'circle') is the external body orifice at the ''exit'' end of the digestive tract (bowel), i.e. the opposite end from the mouth. Its function is to facil ...

to the

genitalia A sex organ, also known as a reproductive organ, is a part of an organism that is involved in sexual reproduction. Sex organs constitute the primary sex characteristics of an organism. Sex organs are responsible for producing and transporting ...

, the underside of the

vagina In mammals and other animals, the vagina (: vaginas or vaginae) is the elastic, muscular sex organ, reproductive organ of the female genital tract. In humans, it extends from the vulval vestibule to the cervix (neck of the uterus). The #Vag ...

, the

clitoris In amniotes, the clitoris ( or ; : clitorises or clitorides) is a female sex organ. In humans, it is the vulva's most erogenous zone, erogenous area and generally the primary anatomical source of female Human sexuality, sexual pleasure. Th ...

or the

scrotum In most terrestrial mammals, the scrotum (: scrotums or scrota; possibly from Latin ''scortum'', meaning "hide" or "skin") or scrotal sac is a part of the external male genitalia located at the base of the penis. It consists of a sac of skin ...

. It is considered medically significant for a number of reasons, in both humans and other animals, including sex determination and as a marker of

endocrine disruptor Endocrine disruptors, sometimes also referred to as hormonally active agents, endocrine disrupting chemicals, or endocrine disrupting compounds are chemicals that can interfere with endocrine (or hormonal) systems. These disruptions can cause ...

exposure. It is regulated by

dihydrotestosterone Dihydrotestosterone (DHT, 5α-dihydrotestosterone, 5α-DHT, androstanolone or stanolone) is an endogenous androgen sex steroid and hormone primarily involved in the growth and repair of the prostate and the penis, as well as the production o ...

, which can be disrupted by

phthalate Phthalates ( ), or phthalate esters, are esters of phthalic acid. They are mainly used as plasticizers, i.e., substances added to plastics to increase their flexibility, transparency, durability, and longevity. They are used primarily to soften ...

s common in plastics. The ''anogenital index'' (AGI) is an index used to compare the AGD relative to a model based on body weight. It is computed as the AGD divided by weight GI = AGD/weight (mm/kg)

Measurement

The AGD is usually measured as follows: from the center of the

to the posterior convergence of the fourchette (where the vestibule begins) in females (AGD-AF); and from the center of the

to the junction of the smooth perineal skin with the rugate skin of the

in males (AGD-AS). An alternative measurement, AGD-AC, defined only in females, is measured from the anus to the clitoris.

In humans

Early studies showed that the human

perineum The perineum (: perineums or perinea) in placentalia, placental mammals is the space between the anus and the genitals. The human perineum is between the anus and scrotum in the male or between the anus and vulva in the female. The perineum is ...

was half as long in females as in males, but it has since been found to be three quarters the male distance in females, although males have more variance. Measuring the anogenital distance in neonatal humans has been suggested as a noninvasive method to determine male feminisation and female

virilization 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 androgens. Virilization is a medical term commonly used in three medical a ...

and thereby predict neonatal and adult reproductive disorders. A study by Swan et al. determined that the AGD is linked to fertility in males, and penis size. * Males with a short AGD (lower than the median around 52 mm (2 in)) have seven times the chance of being sub-fertile as those with a longer AGD. It is linked to both semen volume and sperm count. A lower than median AGD also increases the likelihood of undescended testes, and lowered sperm counts and testicular tumors in adulthood. Babies with high total exposure to phthalates were ninety times more likely to have a short AGD, despite not every type of the nine phthalates tested being correlated with shorter AGD. Swan et al. report that the levels of phthalates associated with significant AGD reductions are found in approximately one-quarter of Americans tested by the

Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the National public health institutes, national public health agency of the United States. It is a Federal agencies of the United States, United States federal agency under the United S ...

(CDC) for phthalate body burdens. Women who had high levels of phthalates in their urine during pregnancy gave birth to sons who were ten times more likely to have shorter than expected AGDs. A 2018 study by Barrett et al. found that infant girls born to women with

polycystic ovary syndrome Polycystic ovary syndrome, or polycystic ovarian syndrome, (PCOS) is the most common endocrine disorder in women of reproductive age. The name is a misnomer, as not all women with this condition develop cysts on their ovaries. The name origin ...

(PCOS) had longer AGD, suggesting higher fetal

testosterone Testosterone is the primary male sex hormone and androgen in Male, males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testicles and prostate, as well as promoting se ...

exposure, than girls born to women without PCOS.

Conditions

Hypospadias Hypospadias is a common malformation in fetal development of the penis in which the urethra does not open from its usual location on the head of the penis. It is the second-most common birth defect of the male reproductive system, affecting about ...

and cryptorchidism are conditions which may be induced in males with short AGD. Other problems in males include risk of testicular dysgenesis syndrome.

In other animals

There have been extensive studies of AGD effects on animals. In some animals, it is routinely measured to determine health. Experiments have demonstrated that in rodent studies this distance is shortened when the mother is exposed to chemicals that are anti-androgenic, such as

dibutyl phthalate Dibutyl phthalate (DBP) is an organic compound of phthalate which is commonly used as a plasticizer because of its low toxicity and wide liquid range. With the chemical formula C6H4(CO2C4H9)2, it is a colorless oil, although impurities often r ...

(DBP) or

benzyl butyl phthalate Benzyl butyl phthalate (BBP) is an organic compound historically used as a plasticizer, which has now been largely phased out due to health concerns. It is a phthalate ester of containing benzyl alcohol, and ''n''-butanol tail groups. Like mo ...

(BBzP).

Bisphenol A Bisphenol A (BPA) is a chemical compound primarily used in the manufacturing of various plastics. It is a colourless solid which is Solubility, soluble in most common organic solvents, but has very poor solubility in water. BPA is produced on a ...

in certain doses increases the AGD of both genders of a study on mice. In 2017, Gobikrushanth et al. studied the relationship between AGD (the distance from the center of the anus to the base of the vagina and the clitoris) and fertility in Canadian Holstein cows. They found that in first and second parity cows an increase in AGD has an inverse correlation with pregnancy success after first artificial insemination. This correlation was not found in third+ parity cows.

References

{{reflist Mammal anatomy fr:Périnée#Distance ano-génitale

Measurement

In humans

Conditions

In other animals

See also

References