Changes in plasma leptin during the menstrual cycle.

OBJECTIVE To measure the plasma concentration of leptin, which is expressed in ovarian follicles and may have a reproductive function, in healthy women during the menstrual cycle. DESIGN This study included nine women with regular menstrual cycles (mean+/-S.E.M. age 28+/-2 years: body mass index 23.9+/-1.8 kg/m2). From the onset of menses, fasting blood samples were collected every 1-2 days throughout the menstrual cycle. As a control, plasma leptin was measured in six postmenopausal women and six men every other day for 28 days. RESULTS In menstruating women, plasma leptin increased from 14.9+/-2.9 ng/ml in the early follicular phase to 20.4+/-4.2 ng/ml (P<0.01) at the midluteal phase and returned to the baseline by the subsequent menses. In contrast, leptin concentrations did not change significantly in postmenopausal women or men. The changes in plasma leptin during the menstrual cycle were not related to changes in sex hormones. CONCLUSIONS The cause of the increase in plasma leptin during the late follicular and luteal phases of the menstrual cycle is not clear. It may be attributed to augmented adipocyte production of leptin in response to increased caloric intake or hypothalamic release of neuropeptide Y. or to release of leptin from mature ovarian follicles. Leptin may have a role in regulating the menstrual cycle and preparing the body for the metabolic demands of pregnancy.