Is atherosclerotic cardiovascular disease an endocrinological disorder? The estrogen-androgen paradox.

The strikingly lower incidence of myocardial infarction (MI) in premenopausal women than in men of the same age suggests an important role for sex hormones in the etiology of MI. Supporting such a role are studies, carried out mostly in men, that report abnormalities of sex hormone levels in patients with MI, correlations of sex hormone levels with degree of atherosclerosis and with levels of risk factors for MI, and changes in the levels of risk factors with administration of sex hormones. Studies have also reported a prospective relationship in men of testosterone level with progression of atherosclerosis, accumulation of visceral adipose tissue, and other risk factors for MI. Puzzling, however, is that neither the level of testosterone nor of estrogen was found to be predictive of coronary events in any of the eight prospective studies that have been carried out. Also puzzling is that whereas the gender difference in incidence of MI would suggest that testosterone promotes and/or estrogen prevents MI, the cross- sectional, hormone administration, and prospective studies have suggested that in men testosterone may prevent and estrogen promote MI. These studies have thus revealed an estrogen-androgen paradox: that endogenous sex hormones may relate both to atherosclerotic cardiovascular disease and its risk factors oppositely in women and men. Recently recognized experiments of nature and their knockout mouse models may present another manifestation of this estrogen-androgen paradox and could help resolve these apparent contradictions.