Gender transition: what happens inside the brain?

Male and female brains are not the same. Male brains have more white matter and are overall bigger. Amongst other things.
So, what happens to the brain of a person who undergoes a gender change?

A study (Hilleke Hulshoff Pol, 2006) found that the brain adapts to the new gender. Following surgery and hormonal treatment of 4 months widespread changes can already be determined.
A dramatic decrease in brain volume in male-to-female transitioned persons was found. The brain lost a minimum of 31 ml, which is the size of a shot glass.
The hypothalamus increased in female-to-male transitioned persons and shrank for men who transitioned to a women.

Besides these anatomical changes, can functional, cognitive and behavioral changes also be found?

  • A study used functional magnetic resonance imaging (fMRI) to investigate brain activity provoked by sexual arousal. After their sex reassignment surgery, male-to-female transsexuals were shown erotic nude pictures of either male or female bodies. The study found that seeing the pictures of men activated wide-spread areas of the brain linked to sexual arousal of male-to-female transsexuals.
  • Changes in cognitive performance were found in another study. Cross-sex hormone treatment resulted in expected gender differences. Three months of estrogen addition and testosterone suppression showed the following results: declined anger, aggression proneness, sexual arousal and spatial ability. On the other hand an increase in verbal fluency was shown.
  • Behavioral alterations have been established in animal studies. Testosterone treatment in female canaries resulted in singing behavior normally only displayed by male canaries.

Did you know that our brains are so incredibly flexible and adaptable?