82 RESPONSIVENESS OF PITUTARY hGH TO CRF IN JUNVENILES WITH SIMPLE OBESITY

It has been found that in obesity the response of plasma hGH to the pharmacological stimuli is blunted and the episodic output of hGH during sleep is also subnormal. The response of plasma hGH to an iv bolus of insulin (4 U/m2) and to an iv bolus of GRF (1 mcg/Kg) too and the response of TSH to an iv bolus of TRH (7 mcU/Kg – 200 mcg maximum dose) were studied in 15 males and females aged 5 – 10 years, all of whom were suffering from severe simple obesity and in 11 normal subjects of the same age. The results (mean and SE) were, in obese: peak plasma hGH to insulin hypoglycemia: 6.5±1.4 ng/ml and to GRF: 10.1±1.9* ng/ml; the peak plasma of TSH to TRH was 18.8±2.5 mU/ml. In the controls they were: 14.0±3.8 ng/ml, 18,3±1.2* ng/ml and 21.6±2.2 mcU/ml respectively. Altough not statistically significant with respect to the controls, hGH response to insulin hypoglycemia was lower in obese subjects and hGH response to GRF was markedly impaired (P < 0.001)*. These data seem to suggest that the decreased response to insulin hypoglycemia in obesity is mediated by an impaired pituitary response to growth hormone – releasing factor.