The way I see it, anyone who has the nerve to ask such a personal question is either a) a very close friend or loved one who feels your relationship is open to communication at such an intimate level, b) someone you know who thinks that because you confided in them about your trans status that it opens up the dialogue to anything and everything having to do with being trans, or c) someone you barely know (or a total stranger!) who doesn't respect you enough to consider how invasive and inappropriate this question is.
In the case of a, they're likely genuinely concerned about your health and well-being.
In the case of b, I'd imagine their tone (how they ask) would give away their motivation for asking such a question.
In the case of c, a harshly worded response would not be unwarranted. A scoff and a glare would be choice. But just walking away would be wise.
It depends on who's asking, and what their motivation for asking may be. Context, motive, tone and your relationship with the asker are all factors imo.
But the bottom line, despite all that, is that it's a freaking rude question and it's nobody's business!
