I remember reading about some psychiatrists tried to use Testosterone on M2F transsexual patients to "cure" GD but got very bad results...
I'm aware of people saying the female and male brains are different but I'm not sure how much of it is innate and how much happens during the development of an individual. After all growing up as a boy or girl means the society has very different expectation/training on him/her, which perceivably affect one's brain development during adolescence. I can understand how HRT might affect the brain chemistry but I have a hard time believe that it actually change the brain construction of an adult, maybe possible to someone in his/her adolescence. Men tend to be more driven and rational but it could be simply because the Testosterone making them more aggressive and eager and less emotional. It may not have anything to do with man was born with a larger some part of the brain...
Another interesting thing is about sexuality (and how hormones change it)... my understanding is that sexuality not only means which sex one finds attractive but also has a lot to do with one's self-image. In that sense gender identity and sexuality are related. This is particularly true in the case of women (cis or trans). I can hard imagine a woman find even the most handsome man attractive if he thinks she looks hideous... The same applies to straight trans-woman. Some of them may not be interested in men at all prior to transition because they were perceived as guys. That does not necessarily mean HRT changed her sexuality -- I'd say transition helped them find their sexuality which was unclear due to gender issues...
