An intersexual is a human or animal who is born with genitalia of indeterminate sex, or which combine features of both sexes.

It is estimated that perhaps 1 percent of live births exhibit some degree of sexual ambiguity. About one in 2,000 births are ambiguous enough to become the subject of specialist medical attention, and the majority of these are subjected to surgery to disguise their sexual ambiguity.

In typical fetal development, the presence of a Y chromosome causes the fetus to develop testes; the absence of a Y chromosome leads to development of ovaries. Thereafter, the development of the internal reproductive organs and the external genitalia is determined by hormones produced by fetal gonads (ovaries or testes) and the cells' response to them. The initial appearance of the fetal genitalia (a few weeks after conception) is very feminine -- a pair of "urogenital folds" with a small protuberance in the middle, and the urethra behind the protuberance. If the fetus has testes, and if the testes produce testosterone, and if the cells of the genitals respond to the testosterone, the outer urogenital folds swell and fuse in the midline to produce the scrotum; the protuberance grows larger and straighter to form the penis; the inner urogenital swellings swell, wrap around the penis, and fuse in the midline to form the penile urethra.

Because there is variation in all of these processes, a child can be born with a sexual anatomy that is typically female, or feminine in appearance with a larger than average clitoris, typically male, masculine in appearance with a smaller than average penis that is open along the underside. The appearance may be quite ambiguous, describeable as female genitals with a very large clitoris and partially fused labia, or as male genitals with a very small penis, completely open along the midline ("hypospadic"), and empty scrotum.

There are dozens of named medical conditions that may lead to intersex anatomy. Fertility is variable. The distinctions "male pseudohermaphrodite", "female pseudohermaphrodite" and especially "true hermaphrodite" are silly vestiges of 19th century thinking that placed "true sex" in the histology (microscopic appearance) of the gonads.

Today, people looking for simple answers are more likely to have faith in the sex chromosomes than in gonadal histology. But in fact, sex is determined by a multitude of factors, and when these factors are inconsistent, no one factor can be thought to determine the "true" sex. Elevating the sex chromosomes above all other factors is the 21st century parallel of the mistake made by the Victorians who located "true" sex in the gonads.

Though high school biology teaches that men have XY and women XX chromosomes, in fact there are quite a few other combinations (XO, XXY, XO/XY, XYY, XX male, XY female), and there are many individuals who do not follow these patterns.

Table of contents
1 Biological causes of intersexuality
2 Chimerism
3 Treatment of intersexuals by society
4 External links and references

Biological causes of intersexuality

Typical men have sex chromosomes XY and typical women XX. One biological definition of a male child is the presence of a Y chromosome. This definition has sometimes been used for gender determination at sports events, but it caused much confusion because it doesn't always apply.

The most common cause of sexual ambiguity is congenital adrenal hyperplasia, an endocrine disorder in which the adrenal glands produce abnormally high levels of virilizing hormones. In genetic females, this leads to an appearance that my be slightly masculinized (large clitoris) to quite masculine.

In many cases invididuals are neither XX nor XY:

One of the most common cases is a fetus with XY chromosomes but where for some reason a fertile male child does not develop. In the following cases the child retains an outward male appearance:
  • Swyer syndrome - damaged testis-determining factor on their Y chromosome.

  • Persistent mullerian duct syndrome: Child has internal uterus and fallopian tubes because Y chromosome fails to produce Mullerian inhibiting factor.

The following further XY cases leads to intersexuality:
  • Androgen insensitivity syndrome. They develop either partially or fully as females, due to their bodies failing to respond to testosterone. In the case of complete androgen insensitivity syndrome (CAIS), their tissues are totally insensitive to androgens, and they will develop as females, with normal female external organs. However, they will not develop a uterus or fallopian tubes, due to the production of Mullerian inhibiting factor by their testes. At puberty breasts will develop due to the production of oestrogen by the testes; but no menstruation will occur due to the lack of a uterus. The tissues of individuals with partial androgen insensitivity, by contrast, have partial sensitivity to testosterone, but it is reduced compared to the male normal. These individuals can develop with either male external anatomy, or female external anatomy, or some combination, depending on the degree of insensitivity.

  • 5-alpha-reductase deficency. In this condition, individuals have testes, as well as vagina and labia, but with a small penis capable of ejaculation instead of a clitoris (this penis, however, appears to be a clitoris at birth). These individuals are normally raised as girls. However, come puberty, their testes will descend, their voice will deepen and they often will develop a male sexual identity. But they develop only limited facial hair.

Excessive in utero exposure to androgens may lead to intersexuality in XX cases:
  • Congenital adrenal hyperplasia: Female internal anatomy, but ambiguous or male external genitalia, and develop male secondary sexual characteristics.

  • Progestin-induced virilisation. In this case, the male hormones are caused by use of progestin, a drug that was used in the 1950s and 1960s in order to prevent miscarriage. These individuals have internal and external female anatomy. They develop however some male secondary characteristics, and they frequently have unusually large clitorises.

A similar phenomenon occurs in cases where a cow brings two fraternal twins, one male and one female, to term. Because (unlike humans) such twins share hormones via their placental blood interface with the mother cow, male hormones produced in the body of the fetal bull find their way into the body of the fetal cow and masculinize her brain. The result is a freemartin (unconventional heiffer), a cow that will eventually try to mount other cows the way that a bull would.


According to the New England Journal of Medicine, vol 338, p 166, physicians in the Western General Hospital of Edinburgh have reported on a child with a penis, one testicle, and an ovary and fallopian tube instead of a second testicle. Some of this child's body cells are XY (male), and some are XX (female). The child was conceived as the result of in-vitro fertilization, and it appears most likely that two embryos, a male embryo and a female embryo, fused before or soon after embryos were transferred to the mother's uterus.

This kind of condition, where there is more than one set of cell lines with different sets of chromosomes making up the body is known as chimerism. This kind of tetraploid chimerism is also found in nature (see New England Journal of Medicine, vol 346, p 1546).

Treatment of intersexuals by society

Intersexual individuals are treated in different ways by different cultures. According to some scholars, there are societies where they have been treated as a third sex, with a social role intermediate between those of men and women. This "third sex" need not exclusively include intersex individuals: the majority of third-gendered or two-spirit aborigional people in North America were/are non-castrated males. One modern-day example of traditional third-gendered people would be the arivanna of India. "Arivanna" is a multilingual umbrella term for feminine eunuchs and similar people; this group consider anyone who is "not a man or a woman" to be part of their community. (These claims have been questioned by some academics.) In most societies, intersexed individuals have been expected to select one sex, and conform to its gender role.

Since the rise of modern medical science in Western societies, intersexuals with ambiguous external genitalia have had their genitalia surgically modified to resemble either male or female genitals. But there are increasing calls for recognition of the various degrees of intersexuality as healthy variations which should not be subject to correction. Some have attacked the common Western practice of performing corrective surgery on the genitals of intersexuals as Western cultural equivalent of female genital mutilation. Despite the attacks on the practice, most of the medical profession still supports it. Others have claimed that the talk about third sexes represents an ideologic agenda to deride gender as a social construct, when in fact it is a biological reality.

Corrective surgery is generally not necessary for protection of life or health, but purely for aesthetic or social purposes. It may lead to negative consequences for sexual functioning in later life, which would have been avoided without the surgery; in other cases negative consequences are avoided by surgery. Defenders of the practice argue that it is necessary for individuals to be clearly identified as male or female, to function socially. However, some intersex individuals have resented the medical intervention, and some have been so discontented with their surgically assigned gender as to opt for sexual reassignment surgery later in life.

The writer Anne Fausto-Sterling coined the words herm (for hermaphrodite), merm (for a pseudo-hermaphrodite that most closely resembles a male), and ferm (for a pseudo-hermaphrodite that most closely resembles a female), and that these be recognized as sexes along with male and female. However, her use was "tongue-in-cheek"; she no longer advocated these terms even as a rhetorical device.

See also: Transgender, Transsexual

External links and references