The estrogen component of OCs: cardiovascular benefits and risks

The relationship of oral contraceptive (OC) use to risk of venous thrombolism, stroke, and myocardial infarction continues to be evaluated. The estrogen component of combination OCs, which is primarily responsible for maintaining the endometrium and minimizing breakthrough bleeding (BTB) and spotting, was the initial focus of clinical and epidemiologic interest following early reports of an increased risk of vascular events with high-estrogen-dose formulations. OC estrogen continues to hold attention; current areas or interest include the relationship of estrogen to laboratory changes in hemostatic, lipid/lipoprotein, and carbohydrate variables, and, more important, to their possible clinical consequences. The historical view that OC-induced lipoprotein changes are responsible for observed increases in vascular risk in OC users is being debated, but the preponderance of evidence suggests that CO-related vascular disease is most likely due to thrombosis rather than atherosclerosis. This issue is made somewhat moot, however, by cumulative epidemiologic data indicating that although some combination OCs containing < or = 35 micrograms estrogen appear to produce a slight increase in the risk of venous thromboembolism, they have no adverse effect on the risk of myocardial infarction and minimal, if any, effect on the risk of stroke. The risks that may be associated with cigarette smoking and concomitant OC use have recently emerged as a somewhat contested issue relative to estrogen dose. Critical examination of the available information suggests that women over 35 years of age who smoke should be advised to use non-estrogen contraceptive methods and that smokers under age 35 may use any OC containing < 50 micrograms estrogen.