[WantAPair]

"During week 1 thru 12, in the absence of any testosterone or a Y chromosome, the fetus will become a female." In other words, the mere existence of a Y chromosome is not enough to produce a male fetus, there must be testosterone in sufficient amount and at the proper time to produce a male fetus.

If I recall correctly, we are ALL female for the first 3 months, then, if we're to become a boy, the T kicks in and the clit becomes the penis, etc., etc.. It's POSSIBLE I suppose, that, in some cases, the T doesn't kick in when it's supposed to and the baby MAY be female a bit longer and maybe that's what makes some a M to F TS. The cognition of being female in the fetuses brain sticks too long and it's already starting to think of itself as female when the T finally kicks in late. So, when he is born, he's already got being female in set in stone in his head. In this scenario, I'm thinking that it's possible that the brain's sexual identification doesn't get turned on until week 12 when the T is SUPPOSED to take affect, but, if it doesn't for a few days, weeks, the brain's sexual ID is already turned and picks up the message (programming, if you will) that it's female. Or, it knows it's female at first and at 12 weeks, the deciding factor (hormones) that tell it whether it is to change to male or not are not yet present, and, at that crucial moment, the brain locks into position as female, but then the body starts to change to male! I'm not quite sure how that could work for a F to M TS. Maybe the fetus HAS the Y, but it just never kicks in, so, even though it's born a girl, it still has this notion SOMEWHERE in it's "programming", BECAUSE of the Y being in there SOMEWHERE, that it was supposed to be a boy. It's just my hypothesis.