Leptin concentrations in semen are correlated with serum leptin and elevated in hypergonadotrophic hypogonadism

Leptin seems to play a role in both food intake and energy balance as well as in the regulation of reproductive features. In order to investigate the regulation of testicular functions by leptin we analysed leptin concentrations in the semen of men with different andrological diseases. It was demonstrated that semen leptin concentrations were inversely correlated with serum testosterone levels and directly with serum leptin concentrations. Furthermore, semen leptin concentrations display only a fraction of serum leptin levels. Semen leptin levels of patients with azoospermia due to hypergonadotrophic hypogonadism, associated with increased follicle-stimulating hormone levels and of high-grade oligozoospermia, were significantly elevated (1.19 +/- 0.46 and 1.09 +/- 0.54 mug l(-1), respectively), while semen levels of leptin in patients with obstructive azoospermia (0.54 +/- 0.41 mug l(-1)) and low-grade oligozoospermia (0.54 +/- 0.34 mug ml(-1)) were comparable with those of normozoospermic men (0.21 +/- 0.21 mug l(-1)). Our data suggest that dysfunction of testicular epithelia as found in hypergonadotrophic hypogonadism and high-grade oligozoospermia with decreased testosterone levels causes elevated spermal leptin concentrations. However, the correlation of semen with serum leptin concentrations indicates that leptin is not actively transported but rather leaks through the blood-testis barrier.