Effects on sex hormone binding globulin of different oral contraceptives containing norethisterone and lynestrenol.
Six combined oral contraceptive drugs containing ethinyloestradiol or mestranol and norethisterone or lynestrenol were studied throughout six 21-day cycles in healthy female volunteers. There was always one menstrual cycle without treatment between every treatment cycle. Plasma levels of norethisterone were determined throughout treatment by use of a specific radioimmunoassay. Sex hormone binding globulin (SHBG) was measured by an ammonium sulphate precipitation method at the beginning and at the end of each treatment cycle. The results indicated an accumulation of norethisterone in plasma when 1 to 3 mg of norethisterone or lynestrenol was given. There was no obvious accumulation during treatment with 0.5 mg norethisterone. SHBG increased during treatment with all combinations studied. However, this increase was most pronounced with the 50 microgram ethinyloestradiol/l mg lynestrenol, 50 microgram mestranol/l mg norethisterone and 35 microgram ethinyloestradiol/0.5 mg norethisterone combinations. There was no statistically significant increase in SHBG with 50 microgram ethinyloestradiol/2.5 mg lynestrenol or 50 microgram ethinyloestradiol/3 mg norethisterone acetate combinations. The results indicated that the induction of SHBG by the synthetic oestrogens was antagonized by the progestogens in a dose-dependent manner. The effect on SHBG by a combind preparation could be one assessment of the oestrogenicity or androgenicity of the preparation.
D000328:Adult; D000510:Alpha-Globulins / Q000378:metabolism*; D003276:Contraceptives, Oral / Q000494:pharmacology*; D003277:Contraceptives, Oral, Combined / Q000494:pharmacology*; D004997:Ethinyl Estradiol / Q000494:pharmacology; D005260:Female; D006801:Humans; D008234:Lynestrenol / Q000494:pharmacology; D008656:Mestranol / Q000494:pharmacology; D009640:Norethindrone / Q000097:blood / Q000494:pharmacology; D011376:Progesterone-Binding Globulin / Q000378:metabolism*
D000510:Alpha-Globulins; D003276:Contraceptives, Oral; D003277:Contraceptives, Oral, Combined; D011376:Progesterone-Binding Globulin; D004997:Ethinyl Estradiol; D008656:Mestranol; D008234:Lynestrenol; D009640:Norethindrone