Effects of oral contraceptives on carbohydrate metabolism.

Both estrogens and progestogens modify carbohydrate metabolism, and their ultimate effect depends upon the ratio of one to the other. The effect of progestogens themselves, which are responsible for increased insulin secretion and for insulin resistance, varies according to their androgenicity but increases according to the series pregnane, estrane and gonane. In contrast, estrogens impair the initial secretion of insulin by the pancreas. The prolonged use of combined oral contraceptives containing the powerful progestogen levonorgestrel is associated with mild but continuing glucose intolerance and with marked insulin resistance.