Spiro is effective both in inhibiting androgenic action at the receptor site, as well as inhibiting T production. The second function is not generally mentioned, I too was previously being ignorant, however after being corrected by a moderator at a chinese TS site, I have done some searching, and did find evidence of such studies. Here's one:
"Healthy male subjects were given orally a single dose of 5 mg canrenone per kg body weight. Canrenone caused a significant decrease in plasma testosterone concentration already 3 hrs after administration of the drug. Suppression of plasma testosterone concentration by 50 to 60 per cent persisted over 9 hrs. It is concluded that suppression of testosterone production is an important factor in the antiandrogenic activity of spirolactones in man."
http://www.springerlink.com/content/rq24p38607370108/Thanks for your recommendation on Lupron, I have not studied Lupron, also it not available here and can be expensive. however, it is not necessary to completely suppressed T production, as there could be benefit of T conversion to E2.