A study of the in vitro metabolism of androgens by human scalp and pubic skin.

The metabolism of dehydroepiandrosterone, androstenedione and testosterone was compared in vitro in human scalp, forehead, pubic and axillary skin biopsies. Conversion of testosterone to the metabolite 5alpha-dihydrotestosterone, believed to be the active form of androgen, occurred in all tissues; however 17-oxosteroids such as androstenedione, 5alpha-androstanedione and androsterone were also formed from testosterone and were the major metabolites of scalp and forehead skin. While 17beta-hydroxy steroid dehydrogenase activity was present in every skin sample, it was evident there were differences in the direction of operation of this enzyme in skin from different body sites. Axillary skin readily metabolised androstenedione and dehydroepiandrosterone to active 17beta-hydroxy steroids such as testosterone and 5alpha-dihydrotestosterone, but these compounds were minor metabolites of androstenedione and dehydroepiandrosterone in forehead and scalp skin despite their activity in 17beta-oxidation of testosterone. Pubic skin was intermediate between axillary and scalp skin in its ability to form 17beta-hydroxy products from androstenedione and dehydroepiandrosterone. It is suggested these patterns of metabolism may reflect differences in androgen sensitivity.