EFFECTS ON SEX HORMONE BINDING GLOBULIN OF DIFFERENT ORAL CONTRACEPTIVES CONTAINING NORETHISTERONE AND LYNESTRENOL

Abstract

Six combined oral contraceptive drugs containing ethinylestradiol or mestranol and norethisterone or lynestrenol were studied throughoout six 21 day cycles in healthy female volunteers. There was always 1 menstrual cycle without treatment between every treatment cycle. Plasma norethisterone levels were determined throughout treatment by a specific radioimmunoassay. Sex hormone binding globulin (SHBG) was measured by an ammonium sulfate precipitation method at the beginning and end of each treatment cycle. The results indicated an accumulation of norethisterone in plasma when 1-3 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. This increase was most pronounced with the 50 .mu.g ethinylestradiol/1 mg lynestrenol, 50 .mu.g mestranol/l mg norethisterone and 35 .mu.g ethinylestradiol/0.5 mg norethisterone combinations. There was no statistically significant increase in SHBG with 50 .mu.g ethinylestradiol/2.5 mg lynestrenol or 50 .mu.g ethylestradiol/3 mg norethisterone acetate combinations. The induction of SHBG by the synthetic estrogens apparently was antagonized by the progestogens in a dose-dependent manner. The effect on SHBG by a combined preparation could be 1 assessment of the estrogenicity or androgenicity of the preparation.