Serum leptin profiles in the normal menstrual cycles and gonadotropin treatment cycles

Circulating levels of leptin, estradiol (E(2)) and progesterone (P(4)) throughout normal menstrual cycles (n = 13), and controlled, stimulated cycles (n = 33) were examined using sensitive specific radioimmunoassays in order to investigate the relationships between sex hormones (E(2), P(4)). Serum leptin levels during the normal menstrual cycle remained constant. However, in the ovulation induction cycle, E(2) levels and circulating leptin levels increased in parallel with the process of stimulation. In addition, leptin/body mass index ratios for all samples were significantly correlated with log(10)E(2). We conclude that particularly high levels of E(2) may have an effect on the secretion of leptin from adipose tissue.