Test to DHT and propecia

Do any of you have a formula of sorts for test to DHT conversion? I just mean, if our body produces..say, 10 mg of test a day, that's 70 mg a week. Now When I shoot Test E 500 mg a week (assuming that shooting test e shuts my HTPA down completely also) that works out to 71 mg of test a day. Ten times what my body is capable of producing. Does that directly and absolutely mean an extra 10 times more DHT? Or does the enzyme or process that transforms test to DHT have it's own limitaions of production? The doses that men with normal test levels don't seem that much different from most BB's I've read. so I have to assume that the seemingly low dose of propecia is enough, or that more propecia means more problems than it's worth. Thanks all for any ideas.