Circulating somatomedin-C levels and the effect of growth hormone-releasing factor on plasma levels of growth hormone and somatostatin-like immunoreactivity in obese children.

The effect of growth hormone-releasing factor (GRF) 1-44 on growth hormone and somatostatin release in plasma has been studied in 20 obese children. Twenty age and sex-matched children with normal weight served as controls. Mean peak growth hormone response in obese children after 1 microgram/kg body wt. GRF 1-44 was significantly lower than in controls (23.7 +/- 3.6 ng/ml vs. 41.1 +/- 3.0 ng/ml; P less than 0.01), as were mean integrated growth hormone response areas (1544 +/- 272 ng X ml-1 X 2 h vs. 2476 +/- 283 ng X ml-1 X 2 h; P less than 0.01). Mean plasma levels of somatostatin-like immunoreactivity did not change after GRF in both groups. Mean somatomedin-C levels in obese children were significantly higher compared to controls (1.6 +/- 0.4 U/ml vs. 0.86 +/- 0.4 U/ml; P less than 0.01). Somatomedin-C levels were not related to the integrated growth hormone responses. In conclusion there is no relation between somatomedin-C levels and the reduced growth hormone-releasing effect of GRF in obese children. GRF does not alter peripheral somatostatin-like immunoreactivity levels either in normal or obese children.