RELATION OF HORMONE-REPLACEMENT THERAPY TO MEASURES OF PLASMA FIBRINOLYTIC-ACTIVITY

Background The mechanisms by which replacement hormones may reduce the risk of coronary heart disease are not fully understood. Of specific interest is a potential effect of replacement hormones on plasma fibri nolytic activity, a putative determinant of thrombotic events. Methods and Results We investigated the relation of current use of replacemen t hormones to three measures of plasma fibrinolytic activity: tissue-t ype plasminogen activator (TPA) antigen, plasminogen activator inhibit or-1 (PAI-1) antigen, and D-dimer. The sample was composed of 288 wome n, free of clinical cardiovascular disease, who were selected for a ca se-control study of atherosclerosis: 142 women with ultrasonographic e vidence of carotid intimal-medial thickening (cases) and 146 control s ubjects. Twenty percent (59 women) reported current use of replacement hormones. TPA antigen and PAI-1 antigen were highly correlated with e ach other (r=.67), whereas D-dimer correlated only weakly with TPA or PAI-1. Compared with nonusers, current users of replacement hormones h ad lower mean levels of TPA and PAI-1 antigens, suggesting enhanced fi brinolytic potential. In the entire sample, the multivariate-adjusted geometric mean values of TPA antigen were 6.3 and 7.3 ng/mL among curr ent users and nonusers, respectively (P=.01); the corresponding values for PAI-1 antigen were 6.1 and 7.5 ng/mL (P=.13). These results were generally consistent for both atherosclerosis cases and their control subjects. D-dimer levels were lower in current hormone users than in n onusers, but the difference was not statistically significant (P>.15) in any of the analyses. Conclusions The use of replacement hormones ap pears to be associated with enhancement of endogenous fibrinolytic pot ential. Enhanced plasma fibrinolytic activity among hormone users may explain, in part, the inverse association between hormone replacement therapy and coronary heart disease.