Melatonin response to TRH in prepubertal and pubertal healthy subjects

The current study was carried out to evaluate the influence of thyrotrophin releasing hormone (TRH) on melatonin secretion in healthy subjects. The study included 31 subjects of both sexes (prepubertal subjects: 15; pubertal subjects: 16). They were treated with TRH (0.2 mg i.v. as a bolus) with blood samples being collected at 0, 20, 60, 120, 180 min. after hormone administration; the results were compared with those of subjects infused with saline only. Serum levels of melatonin were measured with a double antibody RIA method. A significant increase in melatonin levels after TRH was seen only in the prepubertal females, with a peak at 120 min. On the contrary, no significant melatonin changes were seen in the prepubertal males or in either pubertal males and females. These results suggest the existence of sex- and age-related differences in melatonin responses to TRH in humans.