Histopathologycal and topical immunologycal changes in alopeciae

Male pattern hair loss is the most common cause of balding. The pathogenesis involves androgen, and in particular dihydrotestosterone, binding to androgen receptors in the dermal papilla of sensitive hair follicles. Hair follicle sensitivity is genetically determined and shows regional specificity. Androgen stimulation of scalp dermal papilla cells induces transforming growth factor beta (TGF-B) and results in cyclical miniaturization of the entire hair follicle. The resulting hair produced from that follicle is shorter and finer and provides less complete scalp coverage. In contrast androgen stimulation of beard dermal papilla cells produces insulin growth factor -2 (IGF-2) and results in cyclical enlargement of the entire hair follicle. The resulting hair produced from that follicle is longer and thicker and provides more complete facial skin coverage. Some degree of androgenetic alopecia is universal among ageing men, especially bitemporally, however less than half become bald in the Hippocratic sense. Although scalp hair coverage has little functional importance, it has cosmetic significance. Baldness changes the facial appearance of affected men. When that change is perceived as adverse it has the potential to produce emotional morbidity.