The effects of hormone replacement therapy on plasma rheological findings in healthy postmenopausal women.

Abstract

Objective: To investigate and compare the effects of three- and six-month hormone replacement therapy (conjugated equine estrogen plus medroxyprogesterone acetate vs. conjugated equine estrogen) on plasma rheological findings in healthy postmenopausal women.Design: Prospective study.Materials/Methods: In this study, we assigned 30 healthy postmenopausal women to receive sequentially combined 0.625 mg conjugated equine estrogen plus 5 mg medroxyprogesterone acetate daily (n = 17, spontaneous menopause group) or 0.625 mg conjugated equine estrogen (n = 13, surgically menopause group) for 6 months. Plasma and blood viscosity (at three different shear rates), erythrocyte cell deformability (erythrocyte membrane stiffness) were measured in baseline and 3, 6 months samples after study entry. Blood viscosity was measured at natural hematocrit as well as at hematocrit 45%. Plasma viscosity was measured with a Harkness-Viscometer. Whole blood viscosity was measured with a differential speed rotational viscometer and for the measurement of erythrocyte cell deformability a stroboscopic centrifugation method was used.Results: Plasma viscosity was significantly reduced at 3 months in both groups. At 6 months therapy, the statistically significant reduction on plasma viscosity was seen only surgically menopause group (p:0.001). Hormone replacement therapy increased the erythrocyte cell deformability values in both groups. This increase was reached statistically significant in the spontaneous menopause group (p:0.011). There were no significant differences on blood viscosity (at three different shears) in both groups.Conclusions: To our knowledge, this is the first report that evaluates the influence of hormone replacement therapy on erythrocyte cell deformability in postmenopausal women. This study demonstrates decreased plasma viscosity and increased erythrocyte cell deformability in postmenopausal women on hormone replacement therapy. This study suggests an additional mechanism for the cardiovascular protection conferred to postmenopausal women on estrogen replacement therapy. Improved rheology offers a mechanism by which HRT lowers the risk of coronary heart disease. Objective: To investigate and compare the effects of three- and six-month hormone replacement therapy (conjugated equine estrogen plus medroxyprogesterone acetate vs. conjugated equine estrogen) on plasma rheological findings in healthy postmenopausal women. Design: Prospective study. Materials/Methods: In this study, we assigned 30 healthy postmenopausal women to receive sequentially combined 0.625 mg conjugated equine estrogen plus 5 mg medroxyprogesterone acetate daily (n = 17, spontaneous menopause group) or 0.625 mg conjugated equine estrogen (n = 13, surgically menopause group) for 6 months. Plasma and blood viscosity (at three different shear rates), erythrocyte cell deformability (erythrocyte membrane stiffness) were measured in baseline and 3, 6 months samples after study entry. Blood viscosity was measured at natural hematocrit as well as at hematocrit 45%. Plasma viscosity was measured with a Harkness-Viscometer. Whole blood viscosity was measured with a differential speed rotational viscometer and for the measurement of erythrocyte cell deformability a stroboscopic centrifugation method was used. Results: Plasma viscosity was significantly reduced at 3 months in both groups. At 6 months therapy, the statistically significant reduction on plasma viscosity was seen only surgically menopause group (p:0.001). Hormone replacement therapy increased the erythrocyte cell deformability values in both groups. This increase was reached statistically significant in the spontaneous menopause group (p:0.011). There were no significant differences on blood viscosity (at three different shears) in both groups. Conclusions: To our knowledge, this is the first report that evaluates the influence of hormone replacement therapy on erythrocyte cell deformability in postmenopausal women. This study demonstrates decreased plasma viscosity and increased erythrocyte cell deformability in postmenopausal women on hormone replacement therapy. This study suggests an additional mechanism for the cardiovascular protection conferred to postmenopausal women on estrogen replacement therapy. Improved rheology offers a mechanism by which HRT lowers the risk of coronary heart disease.