Sex hormone priming prior to the combined hypoglycaemia test

Increased insulin sensitivity in young, growth hormone deficient children

OBJECTIVE

Although growth hormone (GH) has well documented insulin antagonistic effects, GH deficient adults often demonstrate insulin resistance. In young GH deficient children, increased susceptibility to hypoglycaemia might indicate increased insulin sensitivity; however, this has not been documented. We therefore determined insulin sensitivity in GH deficient and GH sufficient children.

DESIGN AND PATIENTS

Prospective study of children undergoing insulin tolerance tests for clinical investigation of GH or cortisol secretion at a regional Paediatric Endocrine/Growth Clinic between October 1986 and December 1997. Ninety-one tests were performed in children with GH deficiency and 142 tests in children with normal GH response to insulin (peak GH > or = 20 IU/l).

MEASUREMENTS

The standard insulin tolerance test was modified to permit frequent 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 sufficient children (P = 0.004) and had lower glucose nadirs post-insulin (P = 0.005). Subgroup analysis revealed that these differences were greater in younger (< 12 years old) or pre/early pubertal children. In 14 prepubertal children, 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 children with normal GH secretion. This difference attenuated with age and puberty, possibly secondary to pubertal sex steroids; however, insulin resistance as reported in GH deficient adults, was not observed in adolescents.