I've been doing a lot of research on this because I take Saw Palmetto extract which works like finasteride. Fergie is right, it does stop test from converting to DHT. Test can convert to estrogen, but DHT can't, so I can see how theoretically it could hinder your gains. Theory being that all the excess test will convert to estrogen and not DHT. I think if you take an anti aromatase with your cycle, you'd be just fine. As for me, I'm finishing up my first cycle with low doses of sust, and I've gained just about 25 pounds now. I am not taking a-dex or anything either. Admittedly, I do get bloated sometimes (estrogen I assume), but haven't lost any hair, and am pleased with my gains.