The do? I thought they simply reduced the levels of DHT by playing with that enzyme thingie. And I've read unconformed reports that testosterone levels may actually RISE when taking finasteride in an attempt to compensate for the lower DHT levels.
It's all interesting and waaay beyond my knowledge, but the bottom line I can't avoid is that finasteride DID grow back my hair. I stopped taking it and it all fell out again. Now I'm back on it, and I'm guessing the pattern/relationship will continue.