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

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 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.
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.