Androgen Binding Capacity and 5α-Reductase Activity in Pubic Skin Fibroblasts from Hirsute Patients*

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Abstract
We have measured the total (cytosolic plus nuclear) androgen binding capacity of pubic skin fibroblasts from nine patients with hirsutism of various origin. Confluent intact cell monolayers were incubated with increasing concentrations (0.05–2 nM) of [3H]dihydrotestosterone ([3H]DHT) with or without a 200-fold excess of unlabeled DHT. The androgen binding capacities (mean ± SD) were similar in normal men (411 ± 171 fmol/mg DNA), women (310 ± 103 fmol/mg DNA), and hirsute patients (313 ± 141 fmol/mg DNA) regardless of the plasma androgen levels. In contrast, the 5α-reductase level in pubic skin fibroblasts (mean ± SD) was, as previously described, higher in hirsute women (3.3 ± 2.6 fmol/μg DNA·h) than in normal women (1.1 ± 0.6 fmol/μg DNA·h; P < 0.05). We conclude from these data that: 1) increased androgen binding capacity cannot be held responsible for hypersensitivity to androgens in hirsutism; 2) the androgen receptor is not regulated by androgens in human skin, as similar levels are observed in men, women, and hirsute patients; 3) this contrasts with 5α-reductase activity and emphasizes the importance of this enzyme as an amplifier of androgen action in areas where it is stimulated by androgens, such as pubic skin. (J Clin Endocrinol Metab56: 1209, 1983)