If you're a girl who identifies as a boy and vice versa then that's fine, I'll happily treat you as the gender you feel like. It's when people say their quad-gender turtlekin i-identify-as-a-toaster hurr/durr/gargle pronouns and that sex doesn't matter that it gets ridiculous. Yes sex does matter. You may identify as female and had gotten hormone treatment and possibly surgery, but you are still susceptible to male issues, such as prostate cancer, of if you're female to male and do not recognize that a heart attack in a biological woman is different than that of a man. A doctor can't treat you properly if you aren't fully truthful with them, or even remind them that you're transgendered.