My association of being transgendered with being straight was a little garbled. It can get confusing but this is what the APA says:
What is the relationship between transgender and sexual orientation?
The great majority of cross-dressers are biological males, most of whom are sexually attracted to women. People generally experience gender identity and sexual orientation as two different things. Sexual orientation refers to one’s sexual attraction to men, women, both,or neither, whereas gender identity refers to one’s sense of oneself as male, female, or transgender. Usually people who are attracted to women prior to transition continue to be attracted to women after transition, and people who are attracted to men prior to transition continue to be attracted to men after transition. That means, for example, that a biologic male who is attracted to females will be attracted to females after transitioning, and she may regard herself as a lesbian.