Now, sexual preference is not the only thing prenatal hormones influence. Although it is still much disputed, gender identity also seems to be related to the androgens acting on the fetal brain. Genitals and brain do not become sex-specific at the same time -- anatomical differentiation happens in the first three months of pregnancy, while the brain follows a bit later6. Due to the different time-tables it is possible that these two processes take different routes: you might have a vagina but because of a later -- atypical for females -- testosterone surge your brain is imprinted in a male way (we’ll talk more about specific differences in the later sections).

So far the findings are quite inconclusive and messy with only one thing being clear: getting too little or too much androgens before birth most probably influences your sexual preference and/or your gender identity by making certain things in your brain different. So...what exactly is different then?

Differences in the brain

Let’s assume that hormonal/genetic factors played their role and set the brain on a non-straight development course. Now what?

Indeed, studies have found that many regions in gay brains, which normally differ between women and men, look not typical for their sex. It was found that specific regions of hypothalamus -- a region responsible for, among others, reproductive behavior and sexual response -- differ between gay and straight people.

First off, a region called INAH 3 was found to be almost double as large for heterosexual men as compared to their gay counterpart7 (since its publicaion in '91 there was only one moderately successful effort to replicate it though 8). Secondly, hypothalamus of gay men and straight women reacted to pheromones from men’s sweat (yummy!), while pheromones from female urine (it only gets better) induced a response in their smell-processing region only9 (wouldn’t surprise me if after all these sweat and urine the participants activated “leaving this stupid study”-region). Hypothalamus’ involvement doesn’t end at that: one study found that it doesn’t respond to fluoxetine, the common antidepressant, same way in gay men as it does in straight men10. For some reason this study didn’t get much attention although it has a big potential for clinical relevance: if there is a difference in the responsiveness of the serotonergic system (fluoxetine acts on serotonin) then maybe it should be considered when treating gay men with depression?