Testosterone 5alpha-reduction in the skin of normal subjects and of patients with abnormal sex development.

Human pubic skin was obtained from normal subjects and patients with abnormal sex differentiation. Skin samples (200 mg) supplemented with NADPH, were incubated for 1 h with labelled testosterone. The conversion of testosterone to dihydrotestosterone, 3alpha- and 3beta-androstanediol was calculated. This conversion averaged 14.9 plus or minus 3.4% (SE) in 11 normal men and 3.6 plus or minus 1.4% (SE) in 8 normal women. In 4 children as in 4 young hypogonadotrophic hypogonadal men, the conversion rate of testosterone to 5alpha-reduced metabolites was low (0.8 to 3.5%) and increased at puberty (13.5 to 19.2%). After administration of HCG for 3 months to 1 of the hypogonadal men, it reached 30.2%. Inversely, the formation of dihydrotestosterone and androstanediols from testosterone was suppressed in 2 men treated with large doses of oestrogen. In 3 subjects with an incomplete form of testicular feminization syndrome, the conversion rate of testosterone to 5alpha-reduced metabolites was in the normal male range (6.4 to 18.3%), whereas it was low in one case of the complete form of the syndrome (1.5%). In 9 women with idiopathic hirsutism the rate of 5alpha-reduced metabolites recovered from testosterone was close to that of normal men (13.5 plus or minus 5.5% (SE). From these results, it is postulated that in human subjects, there is a good correlation between hair growth in skin from a sexual area and the extent of testosterone 5alpha-reduction in this tissue. Such an enzymatic activity might be induced by active androgens; this latter hypothesis is in good agreement with the increase of 5alpha-reduction activity observed at puberty or after treatment of young hypogonadal males. In addition, it is pointed out that a positive correlation is observed between the 5alpha-reductase activity present in each skin sample studied and the urinary 3alpha-androstanediol found for the same individual. This confirms our previous findings suggesting that the determination of urinary 3alpha-androstanediol might prove of clinical interest in the evaluation of the androgenic status in human subjects.