Acute and chronic effects of hormone replacement therapy on the cardiovascular system in healthy postmenopausal women.

Previous studies have shown that conjugated estrogens and continuous medroxyprogesterone increases heart disease risk in healthy women. Little is known about the effects of the natural ovarian hormones estradiol and progesterone on cardiovascular function at rest and exercise. The purpose of this study was to investigate the short- and longer-term effects of a cyclic format of hormone replacement therapy (HRT) (1 mg estradiol daily with cyclic micronized progesterone, 200 mg for 10 d/month) on cardiovascular function at rest and during exercise in healthy, postmenopausal women. A double-blind, cross-over study was conducted in 31 patients. Peak oxygen uptake and ventilatory threshold in addition to submaximal cardiac output were determined. Peripheral measures of resting and peak ischemic blood flows were also determined. Measurements were made at baseline, after 4 h of estrogen/placebo exposure, and subsequently after 1, 2, and 3 months. The sequence of data collection was repeated after 6-wk washout. Oral estradiol with cyclic micronized progesterone increases peak ischemic peripheral blood flow chronically but fails to improve exercise tolerance and peak oxygen uptake. Similarly, submaximal central cardiovascular function is unaffected by HRT. This suggests that estradiol has a beneficial effect on peripheral blood flow, but this benefit offers little advantage in terms of peak exercise performance after 3 months of HRT.