GROWTH AND GROWTH HORMONE. IV. LIMITATIONS OF THE GROWTH HORMONE RESPONSE TO INSULIN AND ARGININE AND OF THE IMMUNOREACTIVE INSULIN RESPONSE TO ARGININE IN THE ASSESSMENT OF GROWTH HORMONE DEFICIENCY IN CHILDREN

Abstract

The growth hormone (GH) response to insulin-induced hypoglycemia and to arginine infusion has been evaluated in 60 children with growth retardation. These children have been classified into three groups: Group 1-9 children had peak serum growth hormone values of 7 mµg/ml or greater to both stimuli, a normal growth hormone response. Group 2-18 children had peak GH values of ≤ 3 mµg/ml to both stimuli, an abnormal response indicating growth hormone deficiency. Group 3-6 children had a blunted GH response (> 3 < 7 mµg/ml) to both stimuli; 8 showed a normal rise in serum GH following arginine infusion (> 7 mµg/ml) but exhibited no rise, or a minimal one, following insulin administration; 9 children had minimal increase in serum GH concentration following arginine infusion but showed a normal GH response to insulin administration (> 7mµg/ml). Children included in Group 3 represent a heterogenous population. In some patients with a blunted response to both stimuli, evidence of partial or less severe form of GH deficiency was found, whereas in 17 of 18 children exhibiting a disparate response the impaired growth was not attributable to growth hormone deficiency. The blood glucose at all sampling periods was significantly lower following insulin administration in patients in Group 2 than that observed for children in Group 1 and 3. The blood glucose was significantly lower at 90 and 120 minutes following arginine infusion in Group 2 compared to values for patients in Group 1 and 3. Changes in serum insulin in response to the infusion of arginine did not provide a useful index of discrimination among these groups. Administration of diethylstilbestrol, 10 mg/day times 2 days, prior to testing can modify the GH response to both hypoglycemia and arginine; it is a useful ancillary procedure in children with blunted or disparate responses. These studies suggest that two types of stimulation tests are necessary to establish the diagnosis of isolated GH deficiency with a high degree of probability.