Enzymology of the hair follicle.

Androgenetic alopecia (AGA) is the most common type of hair loss in men and women. This continuous process results in a type of alopecia that follows a definite pattern in those individuals who are genetically predisposed. A genetic predisposition is a feature of AGA, but the predisposing genes are still unknown. Our understanding, however, of the hormonal effects on hair growth is far move advanced, and human hair follicles are not only targets for androgens, but also reveal an active androgen metabolism, with the ability to convert several androgens by different steroidogenic enzymes. Recent results suggest that the dermal papilla of the hair follicle expresses abundant type 2 5a-reductase, 3b-HSD and steroid sulfatase activity. Therefore, current information about the androgen metabolism in hair follicles is reviewed and the potential impact on future therapeutic approaches is discussed.