Molecular basis of androgenetic alopecia

Abstract

Androgenetic alopecia is a common, progressive, patterned loss of visible scalp hair. It causes psychological distress and negative effects on the quality of life. Adult levels of circulating androgens and functional intracellular receptors are essential prerequisites for the balding processes. Metabolism of circulating androgens, such as testosterone, to the more potent androgen, 5α-dihydrotestosterone, also appears necessary. Thisalso acts via the androgen receptor. The current model for androgen action in the hair follicle focusses on the mesenchyme-derived, regulatory dermal papilla at the base of the follicle. This responds to the circulating hormones and coordinates the rest of the follicular cells by altering the paracrine signals it produces. These may besoluble growth factors or extracellular matrix components. There is also a strong genetic aspect to the incidence of androgenetic alopecia. Since the response to androgens occurs within the follicle, it can differ. Androgen responses vary from stimulation (e.g. beard), no effect (e.g. eyelashes) to inhibition on areas of the scalp (androgenetic alopecia). This paradoxical difference underpins the successful transplant of unaffected follicles from non-balding regions into the androgen-sensitive, balding areas during corrective surgery for androgenetic alopecia. © 2010 Springer-Verlag Berlin Heidelberg.