If you google male contraceptives and testosterone you can find some info about male birth control pills. Apparently testosterone can work as a contraceptive by shutting down the production of FSH and thus "killing" the sperm count. However one article mentioned that making "the pill" effective for non-asian men required the addition of progestins. Now I don't like the idea of me taking estrogen any more than the thought of my girlfriend taking them, I probably like it even less.
Is there any of the synthetic hormones out there that does an extra good job at making men infertile?