Regulation of human hair growth by steroid hormones. II. androstenedione metabolism in isolated hairs

Andrqstenedione-1, 2-³H metabolism has been measured under standardized conditions in growing and resting hair roots from varying anatomical sites from 5 women and 12 men, 6 of whom had male pattern baldness. 5α-Reduced and 17β-hydroxysteroids were the major metabolites of androstenedione. Hairs from all body regions have the capacity to transform androstenedione into testosterone but the rate of the reduction of 17-ketosteroids is less than the rate of oxidation so that the 17-keto rather than 17β-hydroxysteroids tend to accumulate in the cell. Since the 5α-reduction is irreversible and conditions favor the formation of 17-ketosteroids, androstanedione is the principal intracellular androgen in the hair root.