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.
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Kloosterboer et al. (1987) studied this question.
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