intersex can be divided into 4 categories:
- 46, xx intersex
- 46, xy intersex
- true gonadal intersex
- complex or undetermined intersexuality
- congenital adrenal hyperplasia (the most common cause).
- male hormones (such as testosterone) taken or encountered by the mother during pregnancy.
- Maternal male hormone-producing tumors: most often ovarian tumors. mothers of 46,xx intersex children should be screened unless there is another clear cause.
- Aromatase deficiency: May not be noticed until puberty. aromatase is an enzyme that normally converts male hormones into female hormones. too much aromatase activity can lead to excess estrogen (female hormone); too little for 46, xx intersex. At puberty, these xx boys, who were raised as girls, may begin to take on masculine characteristics.
- problems with the testicles: the testicles normally produce male hormones. if the testicles are not formed properly, it will lead to undervirilization. there are several possible causes for this, including pure xy gonadal dysgenesis.
- problems with testosterone formation: Testosterone is formed through a series of steps. each of these steps requires a different enzyme. deficiencies in any of these enzymes can result in inadequate testosterone and produce a different syndrome of 46,xy intersex. different types of congenital adrenal hyperplasia can fall into this category.
- problems with testosterone use: Some people have normal testicles and produce adequate amounts of testosterone, but still have 46,xy intersex due to conditions such as 5-alpha-reductase deficiency or androgen insensitivity syndrome ( ais).
- People with 5-alpha-reductase deficiency lack the enzyme needed to convert testosterone to dihydrotestosterone (dht). there are at least 5 different types of 5-alpha-reductase deficiency. some of the babies have normal male genitalia, some have normal female genitalia, and many have something in between. most change to external male genitalia around puberty.
- ais is the most common cause of 46,xy intersex. It has also been called testicular feminization. here, the hormones are all normal, but the male hormone receptors are not working properly. There are over 150 different defects that have been identified so far, each causing a different type of AIS.
each is discussed in more detail below.
Note: In many children, the cause of intersex may remain undetermined, even with modern diagnostic techniques.
46, xx intersex
the person has the chromosomes of a woman, the ovaries of a woman, but the external (outside) genitalia appear male. this is most often the result of a female fetus being exposed to excess male hormones before birth. the labia (“labia” or skin folds of the external female genitalia) fuse together and the clitoris enlarges to resemble a penis. In most cases, this person has a normal uterus and fallopian tubes. this condition is also called 46,xx with virilization. used to be called female pseudohermaphroditism. there are several possible causes:
46, xy intersex
The person has the chromosomes of a male, but the external genitalia are not fully formed, ambiguous, or clearly female. internally, the testicles may be normal, malformed, or absent. this condition is also called 46,xy with undervirilization. used to be called male pseudohermaphroditism. the formation of normal male external genitalia depends on the proper balance between male and female hormones. therefore, it requires the proper production and function of male hormones. 46, xy intersex has many possible causes:
true gonadal intersex
The person must have both ovarian and testicular tissue. this may be in the same gonad (an ovotestis), or the person may have 1 ovary and 1 testis. the person may have xx chromosomes, xy chromosomes, or both. the external genitalia may be ambiguous or may appear female or male. this condition used to be called true hermaphroditism. In most people with true gonadal intersex, the underlying cause is unknown, although some animal studies have linked it to exposure to common agricultural pesticides.
complex or indeterminate intersex disorders of sex development
many chromosome configurations other than simple 46, xx or 46, xy can cause disorders of sexual development. these include 45,xo (only one x chromosome) and 47,xxy,47,xxx; both cases have an extra sex chromosome, either an x or a y. these disorders do not result in a condition where there is a discrepancy between the internal and external genitalia. however, there may be problems with sex hormone levels, general sexual development, and altered sex chromosome numbers.
