Rationale for hormone replacement therapy in atherosclerosis prevention.

Progestogens are clearly useful to balance the proliferative effects of estrogens on the endometrium; however, some progestogens have been shown to attenuate the cardiovascular benefits of estrogen, and this has been the subject of considerable debate. Accumulating evidence confirms the deleterious effects of medroxyprogesterone acetate on estrogen's cardioprotective effects and provides new and compelling evidence that not all progestogens are alike in this regard. Maintaining estrogen's cardioprotective effects is strongly dependent upon the type of progestogen and route and method of administration. Numerous periclinical studies conducted on nonhuman primates and other models have demonstrated that certain progestogens, such as micronized progesterone, can be administered concurrently with estrogen replacement therapy, providing protection against endometrial hyperplasia without significantly affecting the beneficial effects of estrogen on lipid profiles, atherosclerosis and vascular reactivity.