Hi Sis,
Not by the classic definitions but we (humans) all start female in utero and then our brains and bodies respond to T to convert us into male, well some of us, present group excluded. There have been a number of publications noting that brain changes in gay people look more female than male, particularly in the hypothalamus. Which as you know is the 'conductor' of the endocrine system. There hasn't to my knowledge been studies on TG people, as getting hold of TG brains for post mortem analysis is probably difficult. And I occasionally use mine so they cannot borrow it.
But I think it is quite clear that we are a form of inter-sexed. There is no good work demonstrating that we have psychiatric problems leading to a 'belief' that we are the wrong gender. There is no evidence that our up bringing has had anything to do with it. Proven in fact by Susan's site, there are TG boys and girls who have brothers and sisters who have been brought up in exactly the same environment and who do not have TG problems. I'm aware of one set of identical twins who went from MtF, which is strong evidence for a genetic link.
There will always be the pretenders and the fetish people who cloud the waters, but in general I think TG is a truly a form of inter-sex, just a bit too difficult to demonstrate at birth.
Do you get inter-sexed ferrets?
Cindy