Comparative studies of the ethynyl estrogens used in oral contraceptives. VI. Effects with and without progestational agents on carbohydrate metabolism in humans, baboons, and beagles.

Human subjects, baboons, and beagles were given cyclic regimens of ethynylestradiol or mestranol; after a number of such cycles, concurrent administration of norethindrone acetate, dl-norgestrel, or megestrol acetate was introduced for a similar number of cycles. Carbohydrate tolerance was evaluated by oral glucose tolerance testing in the human subjects and by intravenous glucose tolerance testing in the baboons and beagles. In the human subjects, neither mestranol nor ethynylestradiol at daily doses of 50 to 100 microgram/day produced any effect on fasting glucose levels or on glucose tolerance even after six cycles of treatment. The addition of the progestational compounds also had no effect on these two variables. In baboons, ethynylestradiol and mestranol were bioequivalent and produced a dose-related decrease in the glucose disposal rate. All three progestational agents counteracted this effect in a comparable manner. In beagles, on the other hand, estrogens produced an increase in the glucose disposal rate, and the addition of progestational agents produced an initial fall and a subsequent return to pretreatment levels.