ASSESSMENT OF THE HYPOTHALAMIC PITUITARY ADRENAL (HPA) AXIS: INSULIN INDUCED HYPOGLYCEMIA VERSUS PAIN

Abstract

To compare the cortisol response to insulin induced hypoglycemia and pain, we carried out a retrospective analysis of 351 short children who underwent growth hormone (hGH) testing with insulin induced hypoglycemia and arginine between 7/75 and 6/92. A venous catheter was placed (pain stimulus) 30 to 60 minutes prior to the test. At 8 a.m. the fasting child received insulin, .05 to .1 unit/kg, (↓ glucose stimulus). A scrum cortisol was measured following pain at 8 a.m. and following insulin at 9 a.m. Children were judged to have an adequate ↓ glucose stimulus if the blood sugar fell 40% and or reached a glucose nadir ≤ 45 mg/dl. Of the children with an adequate ↓ glucose stimulus, 102 were hGH deficient (hGH ≤ 7 ng/ml), while 75 were hGH sufficient (hGH > 10 ng/ml). The peak cortisol level in the hGH sufficient children who had no clinical features of IIPA axis dysfunction was 23.3±7.2 mcg/dl (mean ±1 S.D.) A cortisol response ≥ 9 mcg/dl (mean-2 S.D.) in our hands is the normal response to pain/hypoglycemia, considerably lower than the traditional 18 mcg/dl cutoff established in adults. A peak cortisol value in the 9-18 mcg/dl range may represent partial ACTH deficiency or may be normal (21% of the hGH sufficient children fell in this range).