Nature, nurture, hormones and brains

There’s an interesting article in The Scientist, the magazine for life science professionals, that includes a good round-up of the current research into trans people’s brains. There are lots of fascinating questions:

for people who transition to identifying as a binary gender different from that assigned at birth, “we still also don’t know whether male-to-female and female-to-male transsexualism is actually the same phenomenon, or . . . [whether] you have an analogous outcome in both sexes but you have different mechanisms behind it”…. Other outstanding questions include what, if any, differences there are in the brains of transgender people with different sexual orientations, and between those whose gender dysphoria manifests very early in life and those who begin to feel dysphoric during adolescence or adulthood. [and we don’t know]  whether the brain differences that have been identified between cis and trans people persist after hormone treatment.

Brains are wonderfully complex things, and the mismatch between the gender we’re assigned at birth and the gender we are is likely to be multifactorial: it’s never been as simple as “being born in the wrong body” (which was always a huge oversimplification in an attempt to help cisgender people understand trans people). As one of the interviewees in the piece says, it’s likely to be “a combination between biological, psychological and social factors.”

The more we know, the more we know that we don’t know. For example:

hormone treatments might even affect regions the brain that are not commonly considered to be among those sensitive to sex steroids—specifically, the fusiform gyrus, involved in the recognition of faces and bodies, and the cerebellum, known in part for its role in motor control

There may also be differences in the mechanisms affecting the brains of trans men and of trans women, because while we both take hormones we take different hormones – testosterone for the men and estrogen for the women.

The article concludes:

For now, as is the case for many aspects of human experience, the neural mechanisms underlying gender remain largely mysterious. While researchers have documented some differences between cis- and transgender people’s brains, a definitive neural signature of gender has yet to be found—and perhaps it never will be. But with the availability of an increasingly powerful arsenal of neuroimaging, genomic, and other tools, researchers are bound to gain more insight into this fundamental facet of identity.