CIRCULATING LEPTIN IN WOMEN - A LONGITUDINAL-STUDY IN THE MENSTRUAL-CYCLE AND DURING PREGNANCY

OBJECTIVE To investigate whether leptin is linked to reproduction, cir culating levels were measured longitudinally throughout spontaneous me nstrual cycles and during pregnancy in normal women. DESIGN Longitudin al blood samples were collected from normal volunteers, either during regular menstrual cycles or during successful singleton pregnancies. P ATIENTS Six healthy, regularly cycling, women volunteers (31.5+3.0 yea rs old, BMI=21.6+0.5) were recruited for serial venous blood sampling throughout one complete menstrual cycle. In addition, five healthy, wo men (31.8 +/- 1.2 years old, pre-pregnant BMI=30.0+/-3.1) provided ser ial venous blood samples throughout one complete singleton pregnancy. MEASUREMENTS Circulating venous oestradiol, progesterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), leptin and (pregnant group only) human chorionic gonadotrophin (hCG). RESULTS In spontaneo usly cycling women, changes in circulating leptin levels were associat ed with menstrual phase (P<0.001) and correlated with progesterone lev els (P<0.05). Peak leptin concentrations were recorded during the lute al phase (P<0.01), coincident with maximal progesterone levels (P<0.05 ). Leptin concentrations were elevated throughout gestation (P<0.05), and especially during the second trimester (P<0.05). Post-partum, circ ulating leptin levels fell sharply to below pre-pregnant values. Lepti n correlated with oestradiol (P<0.05) and human chorionic gonadotrophi n (hCG, (P<0.01) levels during pregnancy. First trimester (P<0.05) and postpartum (P<0.05) oestradiol concentrations and post-partum hCG lev els exhibited the greatest correlation with circulating leptin. CONCLU SIONS We conclude that the relationship between body mass index and ci rculating leptin varies during the course of spontaneous cycles in wom en, the best correlation occurring during the luteal phase when proges terone and leptin concentrations are highest. This, together with the correlation between circulating oestradiol, hCG and leptin levels duri ng pregnancy, strongly suggests a dynamic relationship between leptin and reproductive events in women.