PULSATILE PATTERNS OF MELATONIN SECRETION IN PATIENTS WITH GONADOTROPIN-RELEASING-HORMONE DEFICIENCY - EFFECTS OF TESTOSTERONE TREATMENT

Recently, we have demonstrated that male patients with gonadotropin-re leasing hormone (GnRH) deficiency had increased nocturnal melatonin se cretion that decreased to normal levels during testosterone treatment. The purpose of the current study was to examine if the abnormally inc reased melatonin levels in these patients were associated with pulsati le secretory patterns, and, if these were modified during testosterone administration. Characteristics of nocturnal melatonin and luteinizin g hormone (LH) secretion were compared in six normal young males, six males with idiopathic hypogonadotropic hypogonadism (IGD), and in six males with constitutional delayed puberty (DP). Patients were examined in the untreated state and following the administration of 250 mg tes tosterone enanthate/month for 4 months. Serum samples for melatonin an d LH levels were obtained every 15 min from 19.00 hr to 07.00 hr in a controlled light-dark environment. Pulse detection and pulse character istics were determined by the program ULTRA. In comparison with normal controls, untreated IGD patients showed significantly higher pulse fr equency,lower relative increments and shorter half-life times for mela tonin. Similar findings were observed in DP patients, although statist ically of borderline significance. Treatment with testosterone normali zed melatonin pulse characteristics in both IGD and DP patients. The s ecretory pattern of LH release in these patients was characterized by significantly higher relative and absolute increments and shorter half -life time without any significant change in the number of LH pulses. Taken together, these data suggest that melatonin is secreted in a pul satile pattern in normal adult males and in male patients with GnRH de ficiency. The abnormally increased nocturnal melatonin secretion obser ved in these patients may indicate that the pineal pulse generator is expressing an altered activity pattern within its normal capabilities. Testosterone administration normalized melatonin secretory patterns i n IGD and DP patients, The lack of relationship between the pulsatile LH and melatonin secretory patterns suggest an independent signal for the nocturnal pulsatile melatonin and LH secretions.