Melatonina y deficiencia de hormona de crecimiento: contribucin a la evaluacin de los desrdenes neuroendocrinos

melatonin, a hormone secreted by the pineal gland, constitutes a landmark in neuroendocrine integration. the relationship between melatonin and different pituitary hormones and sex steroids has been studied; however, the relationship between growth hormone (gh) and melatonin remains unclear. considering that melatonin is an essential component of the so-called "biological clock", related to circadian rhythm, day-night cycle, and sleep-dependent hormonal alterations, and knowing that physiological gh secretion occurs predominantly at night, we decided to evaluate nocturnal melatonin secretion in a group of gh-deficient children and adults on and off replacement therapy. patients and methods: we studied 44 patients with gh deficiency (ghd), duly confirmed by pharmacological tests, divided into 4 groups: group a (ga ): untreated ghd children; group b (gb): ghd children on gh replacement therapy (0.16 mg/kg/week, stable dose for at least 6 months); group c (gc): untreated ghd adults and group d (gd): ghd adults on gh replacement therapy (0.1- 0.8 mg/day, to maintain igf1 between 0 and +2 sds, stable dose for at least 6 months). all associated hormonal deficits were adequately replaced. melatonin production was evaluated by measuring the excretion of its major urinary metabolite: 6-sulphatoxymelatonin (6-sm). urinary 6-sm was measured (radioimmunoassay, stockgrand ltd, guildford, uk) in nocturnal samples (6pm to 8am) in all patients. results: nocturnal 6-sm levels expressed as μg/unit of time were (mean sem) for the pediatric group: ga = 6.50 ( 5.10) and gb = 8.21 ( 5.31) (mann whitney test, p = 0.82). for adults: gc = 2.99 ( 1.17) and gd = 6.60 ( 2.00) (mann whitney test, p = 0.35). discussion and conclusions: it is difficult to characterize the relationship between melatonin and gh in healthy individuals; however, the administration of intravenous melatonin stimulates gh secretion in normal adults. in some hypothalamic-pituitary alterations, changes in the secretory pa