Hormone replacement therapy reduces the reactivity of monocytes and platelets in whole blood--a beneficial effect on atherogenesis and thrombus formation?

Abstract

Our purpose was to investigate the effects of hormone replacement therapy on the reactivity of monocytes and platelets in whole blood, measured by tissue factor activity, tumor necrosis factor-alpha, and thromboxane B2. Thirty-two women were randomized into either transdermal or oral combined hormone replacement therapy and underwent blood sampling before and after 3 and 12 months of treatment. The tissue factor activity in monocytes was measured both in unstimulated whole blood and after a weak lipopolysaccharide stimulation. Tumor necrosis factor-alpha and thromboxane B2 formation in plasma were measured after a weak lipopolysaccharide stimulation of whole blood. After 12 months of hormone replacement therapy there were significant reductions of tissue factor activity in both unstimulated and lipopolysaccharide-stimulated monocytes (p < 0.001) and significant reductions in the formation of tumor necrosis factor-alpha (p < 0.03) and thromboxane B2 (p < 0.02). There were no differences in these parameters between the transdermal and the oral groups. No changes were observed after 3 months of therapy. Twelve months of hormone replacement therapy reduces cellular activation of blood monocytes and platelets; these changes may account for some of the beneficial effects in reducing the risk of cardiovascular disease.