Leptin, a 16 k-Da protein, has been shown to have roles in diverse physiological processes, such as regulation of body weight and food intake, immune function, hematopoeisis and reproduction. Hypogonadotropic hypogonadism and infertility are common features in leptin deficient ob/ob mice. Exogenous leptin administration increases testicular and seminal vesicle weight, and elevates sperm counts and restores reproductive capacity in leptin deficient mice. Although the effects of leptin deficiency on reproduction are well recognised, the effect of excess leptin on male reproductive function in...