Metabolism and Excretion of C19‐ and C18‐ Steroids by Human Skin

After intravenous administration of [7α-3H]dehydroepiandrosterone [35S]sulfate (3H/35S = 2.88) to a normal male subject various 3H-labeled C19- and C18-steroid metabolites could be isolated from the fractions of free steroids and double-labeled sulfoconjugates (3H/35S = 3.16) in skin extracts, containing a total of 1.36% of the injected 3H-activity. The specific activity of 3H-labeled steroids in skin extracts was found to be significantly lower than that of corresponding compounds in the 24-hour urine. Whereas in skin extracts up to 95% of steroids present were isolated from the fractions of sulfoconjugates, more than 90% of steroids in sweat extracts could be detected in the fraction of free steroids. From such data, as well as from the qualitative and quantitative composition of steroid fractions in skin and sweat it was concluded, that under in vivo conditions endogenous sulfoconjugated dehydroepiandrosterone undergoes a direct metabolism in human skin tissue. Subsequently, sulfoconjugated metabolites probably suffer hydrolysis prior to excretion in sweat.