Abstract
The effects of three low-dose oral contraceptive (OC) combinations on sex hormone binding globulin (SHBG), corticosteroid binding globulin (CBG) and anti-thrombin III activity were studied in 44 healthy fertile women. In one study (study A) the effect of a 21-day monophasic OC combination containing 0.150 mg desogestrel plus 0.030 mg ethinylestradiol (EE) was compared with that of a triphasic combination containing levonorgestrel/EE (6 days 0.050/0.O30 mg + 5 days O.O75/0.040 mg + 10 days 0.125/0.030 mg). In a second study (study B) the effect of a 21-day monophasic combination containing 0.150 mg desogestrel plus 0.020 mg EE was evaluated. Fasting blood samples were taken before treatment, after 3 and 6 (study A only) treatment cycles and 2 months post-treatment (study B only). Each treatment cycle consisted of 21 days of tablet administration followed by a 7-day tablet-free interval. Monophasic desogestrel/EE (0.150/0.030 mg) was found to induce a statistically significantly higher increase in SHBG levels than triphasic levonorgestrel/EE. This difference can be attributed to the lower intrinsic androgenicity of 3-keto desogestrel (the biologically active metabolite of desogestrel) in comparison with levonorgestrel. Monophasic desogestrel/EE (0.150/0.020 mg) induced a similar increase in SHBG to that found with the 0.150/0.030 mg combination. All three preparations induced a twofold increase in CBG levels. Antithrombin III activity did not change with any of the preparations studied, suggesting no effect on the clotting system.