Brain imaging shows that testosterone therapy given as part of sex reassignment changes the brain structures and the pathway associated with speech and verbal fluency. This result supports research that women in general may deal with speech and interaction differently than men.

The sex hormone testosterone exerts a substantial influence on human behaviour and cognition. Previous studies have shown that testosterone has a particular influence on verbal fluency. But these investigations (which due to ethical reasons are mostly observational studies or one-off hormone administrations) have been limited in what they can show, as it has been impossible to follow the direct effect of the hormone on the brain structure.

Now a unique study has revealed the changes over time (longitudinal changes) in the brain of female-to-male transsexuals receiving continuous, high-dose hormone therapy as part of their sexual reassignment.

The results show that this therapy induces structural changes in areas of the brain involved in verbal fluency in female-to-male transsexuals. This may have wider implications, for example in the way that men and women handle speech and interaction.

The researchers, from Vienna and Amsterdam, worked with 18 female-to-male subjects (27.6 ±6.4 years), before and during testosterone treatment. The subjects underwent MRI brain scans before and after 4 weeks of the testosterone administration. The results showed that with testosterone treatment the volume of grey matter decreased in two specific regions of the brain, the Broca’s and Wernicke’s areas, which are mainly responsible for language processing. At the same time, the neuronal pathway…

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