Androgenetic alopecia (AGA) is characterized by a receding hairline
and/or hair loss within a given pattern on the scalp. This disorder, which can
effect both men and women, is an inherited condition, caused by a genetically
predetermined sensitivity in certain scalp hair follicles to the effects of the
androgenic hormone dihydrotestosterone, or DHT. DHT is believed to shorten
the growth, or anagen, phase of the hair cycle, causing miniaturization of the
follicles, and producing progressively finer hairs. The production of DHT is
regulated by an enzyme called 5-alpha reductase (5AR).