Interactions Between Melatonin and Estrogen in the

Authors: Tsuda Kazushi

Publish Date: 2006/10/01

Volume: 19, Issue: 10, Pages: 1092-1092

PDF Link

Abstract

To the Editor We read with great interest the article by Dr Cagnacci and colleagues1 dealing with the vasodilating and hypotensive effect of melatonin in women The results of their study demonstrated that melatonin administration significantly decreased nocturnal systolic diastolic and mean blood pressure BP in women In addition they showed that the effect of melatonin was inversely related to the day–night differences in BP They proposed that melatonin administration may improve the day–night rhythm of BP particularly in women with a blunted nocturnal declineEvidence indicates that both vascular and endothelial function may be markedly influenced by estrogen and could be improved by hormone replacement therapy in postmenopausal women2 In an in vitro study presented earlier we demonstrated that 17βestradiol increased membrane fluidity a reciprocal value of membrane microviscosity of erythrocytes and improved the rigidity of cell membranes in postmenopausal women through the nitric oxide NO and cGMPdependent mechanism3 We also showed that hormone replacement therapy restored the membrane microviscosity and increased the plasma NO metabolite levels in elderly women4 These findings suggest that because abnormalities in membrane microviscosity could cause a disturbance in the rheologic behavior and the microcirculation estrogen deficiency might be involved in the pathogenesis of vascular complications in elderly women In a separate series of the study Cagnacci and colleagues5 showed that melatonin significantly decreased BP and reduced internal carotid artery pulsatility index with a concomitant increase in plasma NO metabolite levels in women taking hormone replacement therapy but not in women not taking hormone replacement therapy These investigators also demonstrated that physiologic doses of estradiol decreased nocturnal BP in normotensive postmenopausal women6 One hypothesis is that melatonin might act synergistically with estrogen and cause vasodilation through the NOdependent mechanism In this context we speculate that changes in sex hormones might modify the cardiovascular responses to melatonin in women Therefore we would like to know the relationship between the magnitude of the melatonin effect and the estrogen status in women in the study of Cagnacci and colleagues Further studies should be performed to assess more precisely the interactions between melatonin and estrogen in the regulation of BP in women

Keywords: