Leptin levels vary significantly during the menstrual cycle, pregnancy, and in vitro fertilization treatment: possible relation to estradiol.

OBJECTIVE: To evaluate the influence of sex steroids on leptin levels in patients with conditions in which the steroid levels are increased. DESIGN: Prospective study. SETTING: A hospital unit for reproductive medicine and a maternal care unit affiliated with the hospital and hospital staff. PATIENT(S): Thirteen women with regular menstrual cycles, 29 women with normal pregnancies, and 25 women undergoing IVF treatment. INTERVENTION(S): Blood samples were obtained during days 1-3, 6-8, 13-15, and 22-25 of the menstrual cycle in regularly cycling women and during gestational weeks 13, 20, 28, 32, and 36 and 7-13 weeks after birth in pregnant women. In women undergoing IVF treatment, blood samples were collected after E2 suppression, after ovarian stimulation, and at the time of ovum pickup. MAIN OUTCOME MEASURE(S): Serum levels of leptin, E2, and progesterone. RESULT(S): Leptin levels varied during the menstrual cycle and were elevated during pregnancy, with a peak during week 28. In the IVF group, leptin levels increased throughout the treatment cycle. Body mass index correlated positively with leptin levels in all three groups, and the maternal weight gain from weeks 13-32 tended to correlate with the rise in leptin levels. Estradiol levels correlated positively with leptin levels during E2 suppression. Negative correlations existed between the pregnancy-induced increases in E2 and leptin levels from weeks 13-32, and between the levels after birth. Leptin levels and progesterone levels did not correlate in any of the groups. CONCLUSION(S): Modest elevations of leptin levels were observed during IVF treatment and pregnancy. The increase in the IVF group indicates that factors other than body fat mass (possibly E2) also are of importance for the regulation of leptin levels.