The accuracy of the glucagon test compared to the insulin tolerance test in the diagnosis of adrenal insufficiency in young children with growth hormone deficiency.

CONTEXT

The accuracy of the glucagon test in the diagnosis of central adrenal insufficiency in young children has not yet been definitively established.

OBJECTIVE

The aim of this study was to investigate the diagnostic accuracy of the glucagon test as an alternative to the insulin tolerance test (ITT) in children with GH deficiency under 6 yr of age.

DESIGN AND SETTING

This was a prospective study conducted in two Pediatric Endocrinology Centers.

PATIENTS AND METHODS

Forty-eight children (median age, 4.2 yr) with GH deficiency confirmed by a peak GH to ITT and arginine less than 10 microg/liter were enrolled: 24 with normal hypothalamic-pituitary anatomy, seven with isolated anterior pituitary hypoplasia, and 17 with structural hypothalamic-pituitary abnormalities at magnetic resonance imaging. Twelve subjects had central adrenal insufficiency defined by a peak cortisol response of less than 20 microg/dl to ITT. All children underwent a glucagon stimulation test with blood sampling for cortisol and glucose (time 0 to 180 min) after the im administration of 30 microg/kg of glucagon.

RESULTS

The mean peak cortisol after glucagon was not significantly different from that obtained after ITT in the whole cohort (25.9 vs. 26.0 microg/dl; P = 0.908), and it was significantly reduced in patients with structural hypothalamic-pituitary abnormalities (P < 0.001). Receiver operating characteristic curve analysis showed that the best diagnostic accuracy was obtained with a peak cortisol cutoff to glucagon of 14.6 microg/dl (sensitivity, 66.67%; specificity, 100%; area under the curve = 0.91; 95% confidence interval, 0.82-0.99). Using this cutoff, 91.67% of the patients were correctly classified.

CONCLUSIONS

This study shows that glucagon is an accurate and safe diagnostic test for adrenal function in young children who are at risk for adrenal insufficiency.