Blood flow variations in internal carotid and middle cerebral arteries induced by postmenopausal hormone replacement therapy.

Abstract

Our purpose was to clarify the mechanisms by which postmenopausal estrogen replacement therapy exerts its protective effect on cardiovascular risk. By means of a bidirectional Doppler ultrasonographic system we measured pulsatility index variations the internal carotid artery and middle cerebral artery in 25 early postmenopausal women during a 6-month period of hormone replacement therapy. Transdermal estradiol (50 micrograms/day) was continuously administered. A 12-day course of medroxyprogesterone acetate (10 mg/day) was added every second month. The pulsatility index showed a significant (p = 0.0001) reduction in both arteries after 6 weeks. At 22 weeks a 25% reduction was measured. No variation of the estrogen-induced pulsatility index reduction was observed at the end of every cyclic progestogen supplementation. In early postmenopausal women hormone replacement therapy causes a rapid reduction of pulsatility index in brain arteries. Cyclical progestational supplementation does not modify this positive effect on reactivity of the blood vessels.