Endocrine Abstracts

The glucagon stimulation test is commonly used to assess the hypothalamic–pituitary axis when the insulin stress test (IST) is contraindicated. The mechanism behind glucagon induced secretion of GH and cortisol is unclear. To determine whether these responses are dependent on symptoms during the glucagon test, a retrospective case note study of glucagon tests performed over 3 years in patients with pituitary disease was undertaken.

Methods: Fifty-six patients underwent a glucagon test. Patients with held glucocorticoid treatment prior to the test on the day of the test. Acromegalic patients were excluded from the GH analysis.

Results: Patients of 78.6% were asymptomatic during the test. Amongst the symptomatic, nausea (50%) and lightheadedness (41.7%) were the most common symptoms. There was no statistical difference in glucose levels between those with and without symptoms during the test.

Peak GH and cortisol occurred at 150–180 min. Glucose nadir was at 240 min. The peak and increment in cortisol secretion from baseline was significantly greater in symptomatic than asymptomatic patients, but no difference was noted with respect to GH between the two groups (Table). IGF1 levels correlated significantly with peak GH level (r=0.38, P=0.008).

Conclusion: The GH and cortisol response during an IST depends on hypoglycaemia and symptoms. Initial conclusions suggest that the GH response during the glucagon test does not appear related to symptoms whereas cortisol does. Cortisol secretion may be in response to either physiological stress or pharmacological effect of glucagon. Baseline IGF1 levels may provide an indication of GH response to glucagon.