Not a man, but have an idea of what to tell potential boyfriends:
" I have PCOS. Basically, that's a reproductive hormone imbalance and it causes x and such outward symptoms."
Then, if he wants to know more, he'll ask questions and you can answer accordingly. You don't even have to say "testosterone", but even if you did, I don't think most men would automatically assume you were transsexual.
In fact, you probably don't have to bring it up at all, unless you were several dates in and considering being intimate. Then, perhaps you'd want to discuss it and why you may feel a little insecure about your appearance. But if you got naked, it would be obvious that you are and always have been a woman. So, Im not suggesting you take off your clothes to prove youre not a tranny, just that, if you get to that point (of intimacy) in a relationship, maybe that's the time to bring up the PCOS. Good luck!