Histologic response to topically applied minoxidil in male-pattern alopecia

Abstract

The histopathology of androgenetic alopecia is characterized by reductions in follicular size and mean hair shaft diameter without significant reduction in follicular density.1 The proportion of hairs found in anagen is diminished with a corresponding increase in hairs in normal telogen, plus a marked increase in a persistent stage of telogen. The telogen germinal unit is the term given by Headington2 to the structure that represents a persistence of telogen after shedding of the club hair but in which anagen has not been re-established.Regrowth of scalp hair following topical application of minoxidil has been demonstrated in both primates3,4 and humans5,6 suffering from androgenetically determined alopecia. As part of a nationwide multicenter trial of topical minoxidil in male-pattern alopecia, scalp biopsy specimens were obtained before and after treatment to determine what histopathologic changes might be found and if this might help us understand the way in which the clinically observed regrowth of hair might occur.