Hence inhibiting the activity of 5_-reductase is one of the approaches for stimulating hair growth.18 The enzyme 5_-reductase is composed of two isozymes: type I providing an optimum pH of 6–9 and type II providing an optimum pH of 5.5.19 Type II 5_-reductase is found in the mustache or in the frontal hair papilla causing male pattern alopecia. On the one hand, since the androgen receptor does not figure in the occipital hair papillary cell, the occipital hair remains even for persons with male-type alopecia. Therefore, it is clear that the adjustment of the androgen sensitivity against steroid type II 5_-reductase has a significant role in the control of male pattern alopecia. Moreover, the fact that finasteride, marketed as Propecia, a specific inhibitor of 5_-reductase type II, is effective in the treatment of male pattern alopecia also bears testimony to this theory.