I certainly take the word of transgender individuals about how they feel to themselves. Prior to birth, boys do get a bump of testosterone, but we don't know yet exactly how that affects the brain. After birth, hormone levels are not exactly the same, but also not enough different to account for little boys being significantly different from little girls in any meaningful way such as being more adept at certain things. There may well be some fundamental differences in male and female brains causing people to either "feel like a woman" or "feel like a man" but there is no evidence that they predetermine who is good at what, or who thinks in a certain way. That is my beef with this type of rhetoric - it's being used to purport that we can split humans into two distinct categories that have no overlap and know all about them based on that alone.