Cross-sex transition therapy changes the shape and functionality of the brain. In monitoring the transition of several patients, brain imaging revealed changes to neural regions and pathways associated with language.

Scientists say the new findings support previous research highlighting differences between the brains of men and women.

Functional MRI analysis showed the brains of 18 female-to-male transitions noticeably changed over the course of their testosterone therapy. Images taken after four weeks and again after four months showed changes in areas of the brain previously linked to speech and verbal fluency.

Prior to the study, researchers recorded baseline measurements of white-to-gray matter ratios in the various regions of each patient's brain. Before-during-and-after imagery revealed the hormone-induced changes.

"What we see is a real quantitative difference in brain structure after prolonged exposure to testosterone," Rupert Lanzenberger, a researcher at the Medical University of Vienna, said in a press release. "This would have been impossible to understand without looking at a transsexual population."

Researchers say the findings could have larger implications, such as helping to explain the differences in how men and women process language and verbal interactions.

"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. "This fits in well with our finding of decreased gray 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 gray matter outweighs the strengthened white matter connection."

The researchers recently presented their findings at the annual meeting of the European College of Neuropsychopharmacology Congress, held this week in Amsterdam.