INCREASED NOCTURNAL MELATONIN SECRETION IN MALE-PATIENTS WITH HYPOGONADOTROPIC HYPOGONADISM AND DELAYED PUBERTY

Hypogonadotropic hypogonadism (IGD) and constitutional delayed puberty (DP) share a common pathophysiologic process, i.e. GnRH deficiency. B oth conditions are heterogenous and exhibit different grades of GnRH d eficiency. To discern whether these disorders of GnRH deficiency are a ssociated with altered melatonin secretion profiles, we compared untre ated young males IGD (n = 7) and DP (n = 7) to normal pubertal male co ntrols in = 6). Serum samples for melatonin, LH, and prolactin concent rations were obtained every 15 min from 1900 h to 0700 h in a controll ed light-dark environment with simultaneous sleep recordings. Mean (+/ - SD) darktime nocturnal melatonin levels were significantly higher in IGD (259 +/- 73 pmol/L) and DP (217 +/- 29 pmol/L) compared with 182 +/- 69 pmol/L in controls (P < 0.02). So were the mean( so) peak melat onin levels (410 +/- 117, 327 +/- 97 and 298 +/- 95 pmol/L in IGD, DP, and controls, respectively (P < 0.05). Integrated nocturnal melatonin secretion values (AUG) mere also higher in IGD and DP (168 +/- 45 and 134 +/- 28) compared with 119 +/- 45 pmol/min . 1 x 10(3) in controls (P < 0.02), The time of melatonin peak and the time of onset of the n octurnal melatonin rise were observed earlier in IGD and DP. Light-tim e mean ct SD) serum melatonin levels were similar in all three groups. No correlations were found between melatonin and LH levels, nor betwe en melatonin and prolactin levels. These data indicate that melatonin secretion is increased in male patients with GnRH deficiency. The lack of correlations between melatonin and LH suggest that circulating sex steroids, rather than LH, modulate melatonin secretion in a reverse f ashion.