There are a few DSDs. These are grouped by the way the gonads (sex glands) form.
With 46XX, the inner organs are female (the ovaries are normal) but the vagina looks masculinized. This is caused by too many male hormones. Some causes are:
- Congenital adrenal hyperplasia: A common DSD. Too many male hormones cause a girl's external sex organs to become too large. The clitoris can grow to look like a penis. Another issue is the vaginal opening may not be visible. Hormone and enzyme levels are off-balance. The body's level of cortisol may be far too low.
- Placental aromatase deficiency: This is from a rare enzyme problem in the placenta. It causes the fetus to get too much testosterone.
- Hormonal medications: Sometimes pregnant mothers are given hormones during pregnancy. They can masculinize the fetus.
- Maternal hormonal imbalance: A pregnant mother can, herself, have a hormone imbalance. This may give the fetus too much testosterone.
With 46XY, the gonads become testes, but the appearance of the penis is unclear. The cause may be from:
- Testosterone biosynthesis defect: One of the testis' five enzymes that usually build testosterone, is missing or low.
- 5a-reductase deficiency: There is a low level of the 5a-reductase enzyme. This enzyme is found in male gonads. Without it, testosterone can't create enough DHT to make male sex organs.
- Partial androgen insensitivity syndrome: In this problem, the cells of the body are only a little responsive to testosterone.
- Complete androgen insensitivity syndrome: In this problem, the body's cells are not responsive to testosterone. The outer genitalia look female.
Disorders of Gonadal Differentiation
In these cases the gonads may not fully develop into testes. There are three types:
- Mixed gonadal dysgenesis: In this case, one gonad stays premature. The other has formed a testis.
- Partial gonadal dysgenesis: The gonads formed some testicular tissue, but not fully. The testes can't work properly.
- Gonadal dysgenesis: In this case, both gonads stay premature. They do not become testes.
In this rare case, the gonads have both ovarian and testicular tissue. Sometimes there is an ovary on one side and a testis on the other.