Effects of TRH administration on plasma leptin levels in infants, children and adolescents.

The aim of this study was to investigate the effect of thyrotropin-releasing hormone (TRH) administration (standard TRH stimulation test) on plasma leptin levels in infants, children and adolescents. Plasma leptin levels were analyzed with regard to age, body mass index (BMI) and results in standard TRH stimulation test. The study population consisted of 79 infants, children and adolescents (age: 4.50 [0.04-20.49] years; BMI: 16.47 [12.46-38.32] kg/m2; BMI SDS: 0.21 [-2.97 to 3.26]) (median [range]). Plasma leptin levels significantly decreased 30 minutes after TRH administration (5 microg/kg; maximum 200 microg i.v.) (p <0.0001). No correlation was found in leptin decrease when comparing the different groups with regard to age, BMI and results in the TRH stimulation test. Positive correlation was found when comparing BMI SDS to plasma leptin levels before (r = 0.74; p <0.001) and 30 minutes after TRH injection (r = 0.73; p <0.001). There was poor correlation when age of patients was compared to plasma leptin levels before (r = 0.46; p <0.05) and 30 minutes after TRH injection (r = 0.47; p <0.05). In summary, we found that TRH administration decreases plasma leptin levels in infants and adolescents independent of age, BMI and thyroid function.