Oral contraceptives and cardiovascular risk. Taking a safe course of action

Abstract

Although a prospective, longitudinal study on the long-term cardiovascular effects of oral contraceptives has yet to be performed, available data are useful in determining a safe course of action while physicians await definitive answers. Exogenous sex steroids produce important effects on lipid metabolism. Early intervention against cholesterol is important in reducing cardiovascular risk. Current users of high-dose formulations, particularly older women who smoke, are at greatest risk for cardiovascular complications, especially myocardial infarction. Low-dose oral contraceptives have more modest effects on lipid metabolism, but important differences in the potency of progestins remain. Fortunately, recent studies among users of lower-dose oral contraceptive formulations fail to show an increase in cardiovascular morbidity and mortality. Nonetheless, prudent physicians will avoid oral contraceptives that may adversely affect lipoprotein metabolism, such as those containing progestins with high androgenic and antiestrogenic potency.

PIP: The cardiovascular effects of oral contraceptives, as predicted by studies on serum lipid changes in users, are based on the progestin dose, androgenic potency and biologic effect of the estrogen in the pill. Women suffer 250,000 deaths per year in the U.S. resulting from cardiovascular disease, almost half as many as men. They have the same risk factors: high cholesterol, high blood pressure and smoking, and also have more risk from diabetes than men do. The serum HDL, especially HDL2, correlates closely and inversely with heart disease risk. Exogenous estrogens raise HDL and HDL2, and lower LDL, conferring protection against coronary disease, in direct proportion to dose. Progestins usually have adverse effects, in proportion to dose, but progestin potency and type also determine their effects. The estrane progestins norethindrone, norethindrone acetate and ethynodiol diacetate are less potent and much less androgenic, while the gonanes norgestrel and especially levonorgestrel are 5-20 times as potent and androgenic. Each pill needs to be considered as a unit. Several comparative studies are reviewed, corroborating the prediction that pills with higher progestin potency have adverse effects on serum lipids, compared to those with higher estrogen effect. For new lower dose multiphasics, the effects either way are minimal, but HDL2 is still significantly lowered by pills containing levonorgestrel. Progestin-only pills lower HDL2 17- 21%. It is prudent to follow and treat the long-term effects of oral contraceptives on blood lipids.