STANDARD AND LOW-DOSE SHORT ADRENOCORTICOTROPIN TEST COMPARED WITH INSULIN-INDUCED HYPOGLYCEMIA FOR ASSESSMENT OF THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS IN CHILDREN WITH IDIOPATHIC MULTIPLE PITUITARY-HORMONE DEFICIENCIES

Insulin-induced hypoglycemia (IIH) is the gold standard test for asses sment of the integrity of the hypothalamic-pituitary-adrenal (HPA) axi s, but it may be hazardous. We sought to determine whether the standar d (250 mu g) or low-dose (1 mu g/1.73 m(2)) short ACTH test can replac e IIH in patients with idiopathic multiple pituitary hormone deficienc ies (MPHD). Three groups of subjects were studied: 1) control group, c hildren with early or accelerated puberty and no other evidence of adr enal or pituitary pathology (n = 13, age 10.1 +/- 2.2 yr, 3 males); 2) patients with idiopathic hypothalamic pituitary insufficiency and eit her isolated GH deficiency or MPHD and preserved HPA function (n = 20, age 13.7 +/- 4.4 yr, 13 males); and 3) MPHD patients with impaired HP A axis function (n = 10, age 16.8 +/- 4.8 yr, 9 males). IIH and the 25 0 mu g and 1 mu g/1.73 m(2) ACTH tests were performed in groups 2 and 3; group 1 underwent only the ACTH tests. Pass peak cortisol level was defined as 520 nmol/L. No significant difference was noted between th e standard and low-dose tests in the 30-min cortisol response to ACTH. Basal and peak cortisol levels attained on both ACTH tests were simil ar in groups I and 2 and significantly lower in group 3 (P < 0.0001). Both the 250 and 1 mu g ACTH tests were highly correlated with IIH (r = 0.71, P < 0.0001 for the 250 mu g, r = 0.7, P < 0.0001 for the 1 mu g, n = 30), and both demonstrated high sensitivity (90% each) and spec ificity (100% and 90%, respectively) compared with IIH. We conclude th at in idiopathic MPHD patients, both the standard and low-dose ACTH te sts are equivalent to IIH in detecting HPA insufficiency. We suggest t hat they can replace IIH as a screening test for the integrity of the HPA suds in children with suspected MPHD.