Sorry I didn't answer some of your questions directed to me earlier. Just now saw them. Megatron has answered them pretty well. Some people have low test due to pituitary problems, which need to be ruled out. Thyroid issues can also be a problem. Also, as someone pointed out, there can be other causes for ED too. I'd suggest trying another endocrinologist, perhaps a young one this time, plus another blood test to be sure. (Sometimes the older doctors learn a lot in their years of practice, but some just get old.) Since your test is not horribly low, and you're young, you might be able to boost your test levels. (I've heard of people boosting their Test production with HCG, for example.) Good luck!