It's also interesting that a large proportion of MtFs appear to be lesbians. I wonder why?
Okay, I'm going to throw this idea out for you to think about (no offense intended, YMMV etc.): it's pretty much accepted that gender identity and sexuality are separate issues that are generated by separate areas of the brain. Right?
So... is it at all possible that the part of the brain that determines gender identity is affected by whatever causes GD; but the part that determines the physical features (i.e. sex) that you'll be attracted to might not be affected by it? This could possibly explain why a lot of transsexuals seem to be attracted to people who present as the opposite of their own birth sex - just like the majority of the population. And why some are attracted to people who are the same as their birth sex. In other words, we're just normal people like anyone else.
Socially speaking, this would make us define ourselves as gay because that is the accepted term for a man attracted to other men, but perhaps it's a bit more complicated than that.
And likewise for MtFs: could some of them have a brain that is 'stereotypically male' in its sexual attraction function but 'stereotypically female' in its gender identity function?
Or perhaps I'm just talking out my backside...