title: Effects of sex steroids on skin 5 alpha-reductase activity in vitro.
abstract: Skin 5 alpha-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 5 alpha-reductase activity. We incubated minces of normal genital and pubic skin with physiologic concentrations of 3H-testosterone to assess 5 alpha-reductase activity by its conversion to 3H-dihydrotestosterone. In separate experiments, 5 alpha-reductase activity was assessed before and after the addition of progesterone, medroxyprogesterone acetate, levonorgestrel, norethindrone, 17 beta-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 5 alpha-reductase activity at 10(-4) mol/L (P less than .01). Medroxyprogesterone acetate, however, failed to affect 5 alpha-reductase activity at similar doses. Estradiol exhibited 40.8 +/- 14.2% inhibition at 10(-4) mol/L (P less than .01), whereas ethinyl estradiol at concentrations from 10(-8) to 10(-4) mol/L failed to inhibit 5 alpha-reductase activity. We conclude that progesterone and the 19-nor-derivatives inhibit 5 alpha-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 5 alpha-reductase activity.
authors.affiliation: Department of Obstetrics and Gynecology, University of Southern California School of Medicine, Los Angeles.
authors.forename: D L
authors.initials: DL
authors.lastname: Cassidenti
authors.forename: R J
authors.initials: RJ
authors.lastname: Paulson
authors.forename: P
authors.initials: P
authors.lastname: Serafini
authors.forename: F Z
authors.initials: FZ
authors.lastname: Stanczyk
authors.forename: R A
authors.initials: RA
authors.lastname: Lobo
mesh_terms: D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000187:drug effects* / Q000378:metabolism*; D058891:5-alpha Reductase Inhibitors; D000328:Adult; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology; D004997:Ethinyl Estradiol / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D016912:Levonorgestrel; D008525:Medroxyprogesterone / Q000031:analogs & derivatives / Q000494:pharmacology; D017258:Medroxyprogesterone Acetate; D008875:Middle Aged; D009640:Norethindrone / Q000494:pharmacology; D009644:Norgestrel / Q000494:pharmacology; D011374:Progesterone / Q000494:pharmacology; D012867:Skin / Q000201:enzymology*; D013256:Steroids / Q000494:pharmacology
chemical_list: D058891:5-alpha Reductase Inhibitors; D013256:Steroids; D009644:Norgestrel; D004997:Ethinyl Estradiol; D011374:Progesterone; D004958:Estradiol; D016912:Levonorgestrel; D017258:Medroxyprogesterone Acetate; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase; D008525:Medroxyprogesterone; D009640:Norethindrone