Intersex

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Female reproductive anatomy

46, XY Intersex. The person has the chromosomes of a man, but the external genitals are incompletely formed, ambiguous, or clearly female. Internally, testes may be normal, malformed, or absent. This condition is also called 46, XY with undervirilization. It used to be called male pseudohermaphroditism. Forming normal male external genitals depends on the appropriate balance between male and female hormones; therefore, enough requires the adequate production and function of male hormones. 46, XY intersex has many possible causes:

• Problems with the testes. The testes normally produce male hormones. If the testes do not form properly, it will lead to undervirilization. There are a number of possible causes for this, including XY pure gonadal dysgenesis.
• Problems with testosterone formation. Testosterone is formed through a series of steps where each 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 in this category.
• Problems with using testosterone. Some people have normal testes, make adequate amounts of testosterone, but still have 46, XY intersex.
  • 5-alpha-reductase deficiency. 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 the time of puberty.
  • Androgen insensitivity syndrome (AIS). This is the most common cause of 46, XY intersex. Here the hormones are all normal, but the receptors to male hormones don't function properly. There are over 150 different defects that have been identified so far, that each cause a different type of AIS. AIS has also been called testicular feminization.

True Gonadal Intersex . Here the person must have both ovarian and testicular tissue. This might be in the same gonad (an ovotestis) or the person might have one ovary and one testis. The person may have XX chromosomes, XY chromosomes, or both. The external genitals may be ambiguous, or may appear to be female or male. This condition used to be called true hermaphroditism. In most people with true gonadal intersex, the underlying cause is unknown, although in some animal studies it has been linked to exposure to common agricultural pesticides.

Complex or Undetermined Intersex . Many chromosome configurations other than simple 46, XX or 46, XY can result in disorders of sex 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.

Review Date: 02/13/2006
Reviewed By: Alan Greene, MD, Chief Medical Officer, A.D.A.M., Inc.