What's utterly fascinating is that the brains of transgender people look like and work like the gender they self-report. It's consistent with the early onset and fixity of their gender identity if it's confirmed to be a brain setting.
If you follow only one link from this bibliography, make it the one to Zhou et. al.'s Nature article.
That said, the remarkable thing about male and female brains is how similar they are. It's a curious phenomenon how hard people will work to "find" differences that aren't actually there.