EFFECTS OF ESTROGEN REPLACEMENT THERAPY ON PERIPHERAL VASOMOTOR FUNCTION IN POSTMENOPAUSAL WOMEN

Hormone replacement therapy is associated with a reduction in cardiova scular events in postmenopausal women. We have recently found that acu te 17 beta-estradiol administration improves endothelium-dependent vas odilation in both the peripheral and coronary circulations of postmeno pausal women. The current study was undertaken in 33 estrogen-deficien t postmenopausal women (mean age 59 +/- 7 years) to determine if short term estrogen replacement therapy also improves endothelium-dependent vasodilation in peripheral circulation. Acute intraarterial infusion of estradiol, which increased forearm venous estradiol levels from 16 +/- 11 to 345 +/- 202 pg/ml, potentiated forearm vasodilation induced by the endothelium-dependent vasodilator acetylcholine by 49 +/- 67% ( p <0.001). Acute estradiol also potentiated vasodilation induced by th e endothelium-independent vasodilator nitroprusside by 5 +/- 31% (p = 0.04). However, after 3 weeks of transdermal estradiol administration (0.1 mg/day), which achieved an estradiol level of 120 +/- 57 pg/ml, t he vasodilator responses to acetylcholine and to sodium nitroprusside were unchanged from initial measurements obtained before acute adminis tration of estradiol, Repeat intraarterial infusion of estradiol in 8 women, while receiving transdermal estradiol, increased forearm venous estradiol levels to 268 +/- 105 pg/ml and again potentiated the vasod ilator response to acetylcholine to a similar degree as that observed in the initial study after acute administration of estradiol. Thus, al though acute intraarterial infusion of 17 beta-estradiol potentiates e ndothelium-dependent vasodilation in the forearms of postmenopausal wo men, this effect is not maintained with a 3-week cycle of systemic est radiol administration. The different effects of acute and chronic estr adiol may be due to the lower plasma levels achieved with chronic estr ogen administration.