Assessing the adrenal axis by the glucagon stimulation test in children with idiopathic growth hormone deficiency

Approximately 30% of children with idiopathic growth hormone deficiency (IGHD) also suffer from other pituitary hormone deficien-cies. Of children with IGHD, approximately 10% are unable to generate appropriate ACTH levels in response to stress. This study was prospectively designed to test the integrity of the adrenal axis in patients with an established diagnosis of IGHD using the glucagon stimulation test (GST). The study population comprised 39 patients with established childhood-onset IGHD. The diagnosis of GHD was established on the basis of failure of GH to increase over 10 ng/ml after two stimulation tests. The GST was performed by intra-muscular injection of 1 mg glucagon. The criteria followed to define adrenal deficiency was cortisol less than 167 ng/l in response to GST. The mean peak blood glucose level was 8.64 ±1.71 mmol/l. Analysing the cohort using the cut-off of 167 ng/ml to define adrenal insufficiency under GST, there were 25.64% of children diagnosed: 20% among males and 35.7% among females. Subjects with GH and ACTH deficiency had a mean peak GH of 2.07 ±1.79 ng/ml – significantly lower than GH peak of children with IGHD alone (p < 0,001). The frequency of children with combined somatotroph and corticotroph deficiencies with a GH peak < 3 ng/ml was 21% (p < 0,001). The current study identified a prevalence of adrenal insufficiency of 25.64%, which could predict greater risk for children if untreated, especially because a substantial proportion of patients do not present clinical symptoms.