Postmenopausal hormone replacement therapy increases coagulation activity and fibrinolysis.

Hormone replacement therapy (HRT) appears to be cardioprotective in postmenopausal women; however, concerns exist over its thrombogenic effects. To address the effects of combined HRT on coagulation and fibrinolysis, we have measured circulating markers of these processes in a double-blind placebo-controlled trial. Forty-two healthy postmenopausal women aged 50 to 75 years received continuous combined HRT with 2 mg estradiol+1 mg norethisterone or placebo for 6 weeks. Hormone profiles were measured at baseline, and lipid and hemostatic parameters were measured at baseline and after 6 weeks of therapy. Baseline characteristics were similar in the 2 groups. With change from baseline the main outcome measure, HRT increased the markers of coagulation (prothrombin fragments 1+2, 0.20+/-0.06 versus 0.06+/-0.04 nmol/L, P=0.0005; soluble fibrin, 2.3+/-0.4 versus 0.25+/-0.3 microgram/mL, P=0.0004), reduced plasma fibrinolytic inhibitory activity (plasminogen activator inhibitor-1, -0.67+/-0.16 versus 0.24+/-0.21 U/mL, P=0.002), and increased fibrinolysis (D-dimer, 24+/-12 versus -6+/-8 ng/mL, P=0.04) compared with placebo. Increases in soluble fibrin and D-dimer were positively correlated (r=0.59, P=0.02), but changes in plasminogen activator inhibitor-1 and D-dimer were unrelated. Although baseline hemostatic and lipid parameters were correlated, there were no associations between changes in hemostatic markers and lipids after treatment. Short-term oral combined continuous HRT (estradiol and norethisterone) increased thrombin and fibrin generation, reduced plasma fibrinolytic inhibitory activity, and increased fibrinolysis. Enhanced fibrinolysis was related to increased fibrin generation but not reduced plasma fibrinolytic inhibitory activity. Coagulation activation may partly explain the increases in venous thrombosis and cardiovascular events reported with the use of combined HRT.