It depends, but they *can.* I took low-dose estrogen-only HRT throughout (no anti-androgens, which are generally considered much MORE damaging to fertility than estrogen) and by 3 years on, I was declared permanently sterile by the pathologist looking at my testicles. You can't go into HRT assuming there's a chance you'll stay fertile; you might, but if you don't plan for the worst-case scenario you could be very disappointed.