My husband started losing his hair a few years back, and he really didn't want to use anything with bad side effects (he was mostly worried about the sexual dysfunction side-effects) so he did some research and found a shampoo/conditioner that has pretty much stopped his thinning (or at least slowed it way down) for the past 8 years or so. He uses something called Pura d'or
It has like 15 DHT blocking ingredients. Seams to do the trick.