LEP and Infertility: In the preovulatory phase (12th day) of the menstrual cycle, a significant correlation of serum leptin was observed with estradiol (r=0.777, p<0.01) and the BMI (r=0.905, p<0.01) in the fertile group, whereas in the infertile group, the serum leptin level was correlated with estradiol (r=0.589, p<0.001) and BMI (r=0.903, p<0.01).