ABNORMAL MELATONIN SECRETION IN MALE-PATIENTS WITH HYPOGONADISM

Recently we have demonstrated that melatonin secretion is increased in untreated male patients with GnRH deficiency. Testosterone administra tion to these patients decreased melatonin secretion to normal levels. These data, however, did not exclude a gonadotropic effect on melaton in secretion. To further elucidate whether gonadal steroids and/or gon adotropins modulate melatonin secretion in humans we compared untreate d young males with hypogonadotropic hypogonadism (IGD, n = 6), and hyp ergonadotropic hypogonadism caused by Kleinfelter's syndrome (KS, n = 11) to normal pubertal male controls (n = 7). KS patients were subdivi ded into two groups: KS-1, with low testosterone; and KS-2, with norma l testosterone levels. Serum samples for melatonin concentrations were obtained every 15 min from 7 PM to 7 AM in a controlled light-dark en vironment with simultaneous sleep recordings. All KS patients had elev ated gonadotropin levels and decreased melatonin levels. Mean (+/-SD) darktime nocturnal melatonin levels in KS-1 were 92 +/- 21 pmol/L and were 146 +/- 46 pmol/L in KS-2 compared with 178 +/- 64 pmol/L in cont rols. Integrated nocturnal melatonin secretion values (AUG) were 64 +/ - 14 pmol/min x L x 10(3) in KS-1 and 96 +/- 29 pmol/min x L x 10(3) i n KS-2 compared with 116 +/- 42 pmol/min x L x 10(3) in controls. All IGD patients had low gonadotropin and testosterone levels. Their darkt ime melatonin levels (286 +/- 26 pmol/L) and the AUC values (184 +/- 1 5 pmol/min/L x 10(3)) were increased. These data indicate that melaton in secretion is increased in male patients with GnRH deficiency and de creased in low testosterone hypergonadotropic hypogonadal patients. Ta ken together, our results suggest that both gonadotropins and gonadal steroids modulate melatonin secretion in humans.