The varying effects of progestins on lipid levels and cardiovascular disease.
A recent study at George Washington University Lipid Research Clinic compared three oral contraceptives containing different progestins and found that increases in total cholesterol, triglycerides, and apoprotein. All were not progestin related. Other effects, however, were apparently dependent on the type of progestin, with the androgenically potent agent dl-norgestrel causing dramatic increases in low-density lipoprotein (LDL)-cholesterol and the ratio of low-density to high-density lipoprotein (HDL) and decreases in HDL, particularly HDL2, and apoprotein Al. Reductions in HDL2 and increases in the LDL/HDL ratio are strongly associated with the development of atherosclerosis. In a study of postmenopausal women receiving hormone replacement therapy, estrogen alone was compared with estrogen plus dl-norgestrel. In contrast to the findings of the previous study, norgestrel lowered LDL and produced less substantial decreases in HDL and HDL2. Thus, although an antiestrogenic effect was evident, it cannot be assumed that the changes associated with progestin-containing oral contraceptives will automatically occur when lower doses of progestin are used in hormone replacement therapy.