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

Abstract

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. Observational cohort study. Alexandria University Hospital. 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. Quantitative clinical assessment as well as laboratory investigations. 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. Postmenopausal women not receiving ERT had the highest levels of plasma orexin A (705.61 +/- 165.62 microg/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 microg/dl). Plasma orexin-A levels were directly correlated with blood glucose lipid profile, arterial blood pressure, and body mass index. 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.