Study: Sex Hormones May Account for ‘Genuine Difference’ Between Male, Female Brains

By Sam Dorman | September 3, 2015 | 4:49pm EDT
Former Olympian Bruce Jenner, who now goes by the name of Caitlyn Jenner, accepting ESPY's Arthur Ashe Courage Award on July 16, 2015. (AP photo)

( - A recent study by researchers at the European College Of Neuropsychopharmacology (ECNP) suggests that sex hormones create a “genuine difference” in brain structure between men and women.

After comparing brain images of 18 female-to-male transsexuals before and after they received testosterone therapy, researchers found that they exhibited significant differences in brain structure after receiving high-dose hormone therapy as part of their sexual reassignment treatment.

Professor Rupert Lanzenberger explained: “What we see is a real quantitative difference in brain structure after prolonged exposure to testosterone.”

“These findings may suggest that the genuine difference between the brains of women and men is substantially attributable to the effects of circulating sex hormones,” Lanzenberger said. “Moreover, the hormonal influence on human brain structure goes beyond early development phases and is still present in adulthood.”

Recent media coverage of transgenderism and transsexualism have raised questions about whether one’s gender can be changed.

In May of 2014, Time Magazine published a cover story dubbing transgenderism “America’s next civil right’s frontier.” In June of this year, former Olympian Bruce Jenner appeared on the cover of Vanity Fair with the request: “Call me Caitlyn.”

As the political support for transgenderism grows, some are even calling for the use of gender-neutral pronouns.  

But this study, which points to innate biological differences between the sexes, calls into question the idea that gender is malleable and independent of biological influences.

According to ECNP Communications Committee member Kamilla Miskowiak, one of the major differences between men and women can be seen in their language processing abilities. The study found that “prolonged exposure to testosterone” affected regions of the brain involved in language and speech.

“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,” Dr. Miskowiak explained.

“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,” she said.

Because researchers studied the influence of testosterone on transsexuals receiving hormone therapy, they were able to study the effect of hormones more directly.

Lanzenberger added: “This would have been impossible to understand without looking at a transsexual population.”

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