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CASSIDENTI DENISE L. MD; PAULSON, RICHARD J. MD; SERAFINI, PAULO MD; STANCZYK, FRANK Z. PhD; LOBO, ROGERIO A. MD
Obstetrics & Gynecology: July 1991
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Skin 5α-reductase activity is the major factor influencing the manifestation of androgen excess. Although oral contraceptives have been useful for the treatment of androgen excess, little is known of the independent effects of the various progestins and estrogens on inhibition of skin 5α-reductase activity. We incubated minces of normal genital and pubic skin with physiologic concentrations of 3H-testosterone to assess 5α-r ductase activity by its conversion to 3Hdihydrotest 'erone. In separate experiments, 5α-reductase activity was assessed before and after the addition of progesterone, medroxyprogesterone acetate, levonorgestrel, norethindrone, 17β-estradiol, and ethinyl estradiol. Progesterone, levonorgestrel, and norethindrone demonstrated 97 ± 5.3%, 47.9 ± 6.3%, and 59 ± 4.6% inhibition, respectively, of genital skin 5α-reductase activity at 10-4 mol/L (P<.01). Medroxyprogesterone acetate, however, failed to affect 5areductase activity at similar doses. Estradiol exhibited 40.8 ± 14.2% inhibition at 10-4 mol/L [P<.01), whereas ethinyl estradiol at concentrations from 10-8 to 10-4 mol/L failed to inhibit 5α-reductase activity. We conclude that progesterone and the 19-nor-derivatives inhibit 5a-reductase activity at high doses, whereas medroxyprogesterone acetate does not. Therefore, the 19-nor-progestin component may expand the usefulness of oral contraceptives in the treatment of hirsutism by an inhibitory action on skin 5a-reductase activity

© 1991 The American College of Obstetricians and Gynecologists