Androgen insensitivity

All fetuses develop along similar lines until about 7 weeks into pregnancy, when androgen hormones trigger the development of male characteristics. But what happens when someone is immune to androgen?

Photo by Christopher Macsurak [CC BY]
Okay, I’m going to say at the outset that I know this is a politically fraught topic, even though it shouldn’t be. I’m going to try to be as sensitive and careful as possible in writing about it.

Intersex individuals are those for whom our classic definitions of male and female do not really work. There are a range of possible reasons for this, and today I want to write about one in particular: Complete Androgen Insensitivity Syndrome.

First, one quick glossary item: genotype refers to a person’s genetic information (i.e. DNA), and phenotype refers to the physical or behavioral result in that person. Most people with XX chromosomes (their genotype) have a female phenotype. Most people with XY chromosomes have a male phenotype. The specific mechanism is this: a gene on the Y chromosome triggers the creation of testes, and those testes produce androgens like testosterone that trigger the creation of the other male sexual characteristics.

However, some people are immune to androgens. The hormones simply have no effect on them. None of those other male sexual characteristics develop. In fact, the androgen turns into estrogen and female sexual characteristics develop instead. (Some people are also partially immune to androgen, which is why this is called Complete Androgen Insensitivity Syndrome.)

The result is this: a person who has XY chromosomes but a female phenotype. Most are physically indistinguishable from women with XX chromosomes and most identify as women. Belgian model Hanne Gaby Odiele (pictured above) is the public face of Androgen Insensitivity Syndrome.

Women with Complete Androgen Insensitivity Syndrome are infertile and can have other internal medical complications, but are typically perfectly healthy – and happy, I hope!

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