Hormone Replacement Therapy and Coronary Endothelial Function in Postmenopausal Women

Abstract

Dr Singh raises some excellent points, and we appreciate his comments. For the sake of brevity, we did not include the number of patients taking progesterone alone. Eighty-two patients took estrogen alone, and 19 took a combined estrogen plus progesterone preparation. However, we did note that concurrent administration of progesterone was not significantly associated with a change in the coronary blood flow or the coronary artery diameter response to acetylcholine or the coronary velocity reserve response to adenosine. Dr Singh's second point is an important one in that calcium channel blockers can affect vasomotor tone. For brevity, we did not include these data in our article. However, there was no significant difference in the rate of calcium channel blocker use between premenopausal and postmenopausal women (P=.52). The rates were also similar between postmenopausal women who were not receiving HRT compared with those who were (P=.17) and compared with those who had received HRT for more than 2 years (P=.20). Furthermore, there was no evidence of an interaction between calcium channel blocker use and any of the 3 comparisons (premenopausal vs post-menopausal, HRT vs no HRT, and HRT for more than 2 years vs no HRT) with regard to percent change in coronary blood flow in response to acetylcholine, percent change in coronary artery diameter in response to acetylcholine, or coronary velocity reserve response to adenosine: all interaction tests yielded P>.20. Dr Singh's final point is interesting. Age certainly could contribute to the observed differences, and it is possible that estrogen has different physiological effects in postmenopausal compared with premenopausal women. Recent animal study data from researchers at the Medical College of Georgia show that, when the activity of nitric oxide synthase that produces nitric oxide is blocked, the administration of estrogen causes not vasodilation but vasoconstriction.1White RE, HanG, Fulton D, Barman S. Dual and opposite effects of estrogen on coronary arteries mediated by type 1 (N) nitric oxide synthase via nitric oxide and superoxide. Presented at the American Heart Association Second International Conference on Women, Heart Disease, and Stroke; Orlando, Fla; February 16-19, 2005.Google Scholar Theoretically, since nitric oxide production is reduced in older women, giving postmenopausal women estrogen might, in this context, be expected to have detrimental cardiovascular effects, as seen in trials such as the Heart and Estrogen/progestin Replacement Study (HERS) and the Women's Health Initiative. Obviously, the physiology of HRT remains incompletely understood, and further study is needed to elucidate the different effects of estrogen on young vs older coronary arteries. Hormone Replacement Therapy and Coronary Endothelial Function in Postmenopausal WomenMayo Clinic ProceedingsVol. 80Issue 6PreviewTo the Editor: I read with interest the article by Halligan et al1 about the effects of long-term hormone replacement therapy (HRT) on coronary endothelial function in postmenopausal women that was published in the December 2004 issue of the Mayo Clinic Proceedings. Although the authors reached interesting conclusions, a few discrepancies should be addressed. Full-Text PDF