Evidence against growth hormone-releasing factor deficiency in children with idiopathic obesity

Abstract

Abstract The mechnisms whereby growth hormone (GH) secretion is decreased in human obsity remain obscure. We studied the response of plasma GH and prolactin (PRL) to an I.V. dose of 0.5 mcg/kg of growth hormone releasing factor (GRF) in three groups of children: lean (N=12), obese (N=15) and GRF-deficient, i.e. children with complete GH deficiency on the basis of conventional provocative testing and evidence of hypothalamic dyfunction on the basis of thyrotropin-releasing hormone testing (N=7). Mean (±SEM) peak plasma GH after GRF was blunted to the same extent in obese and in GRF deficient children (11.1 ± 2.2 and 8.3 ± 2.8 mg/ml) as compared to lean control children (34.7 ± 4.7 mg/ml). The pattern of PRL response to GRF was however different in GRF after GRF injection, and in obese and lean children, who had no acute change in PRL levels after GRF. Baseline plasma somatomedin C concentrations were low for age in GRF deficient children and tended to be high for age in obese children. On the basisi of these discrepant patterns of response of PRL to GRF and plasma somatomedin C concentration, we conculde that GRF defeciency does not account for the decreased GH secreation observed in obese children.