Testosterone Changes the Brain of Transsexuals: How it Impacts Speech

First Posted: Aug 31, 2015 07:22 AM EDT

Those who are transsexual may be dealing with a different set of brain chemicals. Brain imaging has shown that testosterone therapy given as part of sex reassignment changes the brain structures and pathway associated with speech and verbal fluency.

Female-to-male transsexuals undergo testosterone therapy as a part of sex reassignment. Yet very little work has been done on how testosterone therapy can impact the brain. In this latest study, the researchers scanned 18 female-to-male volunteers before and during testosterone treatment.

"It has been known for some time that higher testosterone is linked to smaller vocabulary in children and that verbal fluency skills decrease in female-to-male transsexuals after testosterone treatment," said Andreas Hahn, one of the researchers, in a news release. "This fits in well with our finding of decreased grey matter volume. However, the strengthening of the white matter in these areas was a surprise. We think that when it comes to certain language skills, the loss of grey matter outweighs the strengthened white matter connection."

The researchers found a real quantitative difference in brain structure after prolonged exposure to testosterone. Grey matter decreased in two specific regions of the brain, which are mainly responsible for language processing. At the same time, the white matter connecting the two regions actually became stronger.

"It is well-known that language development differs between girls and boys and that this is related to gender-related differences in brain maturations," said Kamilla Miskowiak, one of the researchers. "However, this intriguing neuroimaging study of transsexuals before and after their female-to-male gender reassignment suggests that even adult men and women differ in brain structure within regions involved in language and speech. In particular, female-to-male gender reassignment resulted in local brain matter decrease within language processing regions which may explain why verbal abilities are often stronger in women."

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