5α-Reductase Activity in the Human Hair Follicle Concentrates in the Dermal Papilla

The 1998 study focused on the enzyme 5α-reductase, which is involved in converting testosterone to the more potent androgen dihydrotestosterone (DHT), and its distribution within human hair follicles. The researchers discovered that the enzyme's activity was significantly higher in the dermal papilla compared to other parts of the hair follicle, with at least 14 times more activity in the scalp and at least 80 times more in the beard. The dermal papilla lacked the enzyme 17ß-hydroxysteroid-dehydrogenase (17ß-HSD), which is necessary for further metabolism, leading to an accumulation of 5α-DHT. In contrast, the root sheath keratinocytes had low 5α-reductase but high 17ß-HSD levels, producing mainly androstenedione. The connective tissue sheaths expressed both enzymes, resulting in a mix of metabolites. These findings indicate that the dermal papilla is a key player in the androgen response of hair follicles, which could have implications for treating conditions like male-pattern baldness. The study included 21 male scalp samples, 6 female scalp samples, and 2 male beard samples.