Plasma orexin-A levels in postmenopausal women: Possible interaction with estrogen and correlation with cardiovascular risk status

Abstract

Objective To assess plasma orexin-A levels in a group of postmenopausal women not receiving estrogen-replacement therapy (ERT), and to compare the values with a group on ERT and a group of reproductive-age women, and to correlate the findings with some cardiovascular risk factors. Design Observational cohort study. Setting Alexandria University Hospital. Population Ninety women, in three groups: a control group of 30 healthy, reproductive-age women, 30 healthy postmenopausal women not receiving ERT, and 30 healthy postmenopausal women on ERT for 6 months. Methods Quantitative clinical assessment as well as laboratory investigations. Main outcome measures Orexin-A levels, serum estradiol, cholesterol, triglycerides, and fasting glucose are the main laboratory outcome measures, whereas blood pressure and weight are the main clinical outcome measures. Results Postmenopausal women not receiving ERT had the highest levels of plasma orexin A (705.61 ± 165.62 μg/dl). Postmenopausal women on ERT had orexin-A levels that were comparable with the control group (233.90 ± 54.26 versus 243.81 ± 68.88 μg/dl). Plasma orexin-A levels were directly correlated with blood glucose lipid profile, arterial blood pressure, and body mass index. Conclusions Higher orexin-A levels are associated with hypoestrogenism, and are partially reversed by ERT. A possible inhibitory effect of estrogen on orexin might partially account for its cardioprotective effect. © RCOG 2010 BJOG An International Journal of Obstetrics and Gynaecology.