Objective:The aim of the present study was to evaluate possible variations in cardiac hemody-namic parameters related to the natural changes of ovarian estrogen production.Methods:Forty postmenopausal women aged 52.7 ± 4.6 years, randomized into two groups (20 patients in each group) according to the administration (group A) or not (group B) of estroprogestin replacement therapy (ERT), were examined using thoracic electrical bioimpedence.Results:After 6 months of therapy, we observed the following: (1) the mean end-diastolic index was significantly higher in group A than in group B (70.27 and 57.13 mL/m2, respectively) (p < 0.05); (2) the mean acceleration index, indicator of heart contractility, and the mean cardiac index rate, indicators of cardiac performance, were significantly higher in group A than in group B (mean, 1.35 vs. 0.76 s [p < 0.01] and mean, 3.22 vs. 2.34 L/min/m2[p < 0.05], respectively); and (3) the patients treated with ERT showed systemic vascular resistance index values significantly lower than the controls (mean, 2280 vs. 3150 f Ohm/m2[p < 0.01]), achieving standard levels after 6 months of therapy. Furthermore, the acceleration index showed a significant increase, within group A, between the third and sixth month of ERT (0.91 vs. 1.35 s [p < 0.05]).Conclusions:Our findings suggest that postmenopausal women treated with a 6-month course of ERT have significantly improved end-diastolic index, heart contractility index, cardiac index, and systemic vascular resistance, whereas 3 months of ERT does not seem to induce the same effects. In our study, thoracic electrical bioimpedence was shown to be a sensitive and specific method of analysis with a very low cost of administration.