Increased insulin sensitivity in young, growth hormone deficient children

OBJECTIVE Although growth hormone (GH) has well documented insulin antagoni stic effects, GH deficient adults often demonstrate insulin resistance. In young GH deficient children, increased susceptibility to hypoglycaemia migh t indicate increased insulin sensitivity; however, this has not been docume nted. We therefore determined insulin sensitivity in GH deficient and GH su fficient children. DESIGN AND PATIENTS Prospective study of children undergoing insulin tolera nce tests for clinical investigation of GH or cortisol secretion at a regio nal Paediatric Endocrine/Growth Clinic between October 1986 and December 19 97. Ninety-one tests were performed in children with GH deficiency and 142 tests in children with normal GH response to insulin (peak GH greater than or equal to 20 IU/l). MEASUREMENTS The standard insulin tolerance test was modified to permit fre quent measurements of glucose (0, 5, 10, 15, 20, 30, 45, 60 and 90 minutes) . Rate of log glucose disappearance in the first 15 minutes was calculated as a direct measure of insulin sensitivity. RESULTS GH deficient children were more insulin sensitive than GH sufficien t children (P = 0.004) and had lower glucose nadirs post-insulin (P = 0.005 ). Subgroup analysis revealed that these differences were greater in younge r (< 12 years old) or pre/early pubertal children. In 14 prepubertal childr en, exogenous sex steroid priming resulted in lower insulin sensitivity (P < 0.05) compared to nonprimed tests. CONCLUSIONS Young GH deficient children were more insulin sensitive than ch ildren with normal GH secretion. This difference attenuated with age and pu berty, possibly secondary to pubertal sex steroids; however, insulin resist ance as reported in GH deficient adults, was not observed in adolescents.