5α-Reductase Activity in the Genital Skin of Hirsute Women*

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Abstract
A simplified, rapid, and highly reproducible technique is described for measuring 5α-reductase activity (5αRA) in small skin biopsies. Human genital skin was obtained from 23 nonhirsute and 20 hirsute premenopausal women (HW) and 5 normal men. Skin samples were minced at 4 C and incubated (with RPMI-1640 in the presence of 95% O2-5% CO2 and 4.15 nmol [14C]testosterone ([14)C]T) for 2 h at 37 C. Steroids were extracted with diethyl ether and separated by Celite and paper chromatography. Radioactivity in specific eluates was quantified, and the mass of each steroid was measured by RIA. The separate formation of 5α-androstane-17β-ol-3-one (DHT), 5α-androstane-3α, 17B diol (3αdiol), androstene-dione, and androsterone from [14C]T was measured. In separate experiments it was demonstrated that an incubation time of 2 h was optimum and that the addition of cofactors was unnecessary. Radiochemical purity was confirmed after chromatography. The mean ± SE conversion ratio (CR) of T to DHT (in 2 h) in HW was higher than that in normal women (16.80 ± 1.62% us. 4.48 ± 0.36%; P < 0.01). In men, the CR of T to DHT averaged 31.60 ± 3.96%. Individual values for the CR of T to DHT in HW and normal women did not overlap. The CR of T to 3adiol was significantly higher in HW (9.66 ±0.86%) and men (15.98 ± 2.0%) compared to that in normal women (2.96 ± 0.32%; P < 0.05). The CR of T to androstenedione was significantly greater n i HW and men (6.18 ± 0.42 and 7.28 ± 1.92%) compared to that in normal women (2.64 ±0.64%; P < 0.05). The CR of T to androsterone was very low and was similar in the three groups. The production of DHT in HW (4.50 ± 1.0 pmol⁄mg-2 h) was significantly greater than that in normal women (0.48 ± 0.08; P < 0.01) and was similar to the production in men (6.18 ± 1.94 pmol⁄mg-2 h). There was a significant correlation between the CR of T to DHT and DHT production, and the CR of T to 3αdiol and 3αdiol production as well as between the CRs of T o t DHT and T to 3adiol. These data suggest that measurements of DHT formation are best suited for the assessment of 5aRA and that the measurement of 5αRA in vitro from small skin biopsies is suitable for the clinical evaluation of hirsutism.