Effects of ethinyl estradiol combined with desogestrel and cyproterone acetate on glucose tolerance and insulin response to an oral glucose load: a one-year randomized, prospective, comparative trial.

To investigate the effects of two slightly estrogen-dominant, monophasic, low-dose oral contraceptives on carbohydrate metabolism, 40 healthy young women were randomly allocated to receive either 30 micrograms of ethinyl estradiol + 150 micrograms of desogestrel, a 19-nortestosterone-derived progestin (Marvelon; n = 21) or 35 micrograms of ethinyl estradiol + 2 mg of cyproterone acetate, a 17-acetoxyprogesterone derivative (Diane-35; n = (19) for a prospective observation period of 1 year. At baseline, 6, and 12 months, blood glucose, plasma insulin, and plasma C-peptide levels were measured during an oral glucose tolerance test. Although the changes were absent (Marvelon) or minimal (Diane-35) at 6 months, both groups had a slight increase in blood glucose levels at 12 months; overall glucose tolerance remaining, however, within the normal range. Plasma insulin levels remained unchanged in the Diane-35-group, which suggested increased insulin resistance, but were significantly decreased in the Marvelon group despite significant rises in plasma C-peptide levels. Comparison of plasma C-peptide and insulin changes suggests enhanced pancreatic insulin secretion and increased hepatic insulin metabolism with both Marvelon and Diane-35.