Off-Topic General Discussion - Page 303

MtF transsexuality is seen once for every 10,000 people, and FtM transsexuality once every 30,000. Gender issues arise very early in development, mothers tell that their son wore his mother's clothes and shoes from early on, mostly was interested in girl toys and mostly played with girls too. But not every child with gender issues will want to change their sex later on.
All evidence points to gender issues arising early on in the womb. Small changes have been found in genes that are involved in hormonal influence on brain development, that increase the chance of transsexuality. Abnormal hormone levels of the child during pregnancy and medicine that the mother takes during pregnancy can increase the odds of transsexuality too.
Sexual differentiation of the genitals happens in the first months of pregnancy, the sexual differentiation of our brain happens in the second half. Because these processes happen at different intervals, the theory exists that with transsexuality these processes have been influenced independently of eachother. If that were to be true you would see female brain structure in MtF transsexuals and male brain structure in FtM transsexuals. In 1995 we found such a structure indeed, in the brain of a deceased donor. We published that in Nature. It was the Bed Nucleus of the Stria Terminalis (BST), a brain structure involved in many aspects of sexual behaviour. The central part of this Nucleus, the BSTC, is twice as big for men and has twice as many neurons. MtF transsexuals had a female BSTC. The one FtM transsexual that we could study - even rarer material than the brains of MtF transsexuals - did indeed have a male BSTC.

When you publish something like that, people want an independent party to back it up. So Ivanka Savic in Stockholm published a study with functional brain scans on living MtF transsexuals. They didn't have surgery yet nor had they received any hormones. She gave female and male pheromones, which caused different stimulation patterns in the hypothalamus for the control group women and men. The stimulation pattern of MtF transsexuals was inbetween that of men and women. Last year Ramachandran came with a interesting hypothesis and preliminary research results on transsexuality. His idea is that for MtF transsexuals the representation of the penis is missing on the cerebral cortex and with FtM transsexuals the area for the breasts wouldn't have been created during development, and that is why they didn't recognize those organs as their own.