Endocrine Abstracts

The low-dose (1 μg) ACTH stimulation test or glucagon stimulation test (GST) are candidate tests for hypothalamo-pituitary-adrenal (HPA) axis evaluation in patients with pituitary disorders. In this study, we aimed to compare the combination of low-dose ACTH and GSTs (named as combination test) with each test results alone in the evaluation of HPA axis in patients with pituitary disorders whether combination test may overcome the problems when the test results are equivocal.

Patients and methods: Forty-one adult patients with pituitary disorders and 20 healthy subjects were included in the study. Patients with diabetes mellitus or with the diagnosis of Cushing’s syndrome were not included in the study. Low-dose ACTH test, GST and combination tests were performed on separate days. Blood samples for the measurement of cortisol were obtained in the basal state and at 30, 60, 90 and 120 min after the administration of 1 μg ACTH intravenously. The lowest peak cortisol value of control subjects (14.6 μg/dl) was considered as the cut-off value for adrenal insufficiency in low-dose ACTH test. The GST was performed by subcutaneous injection of 1 mg glucagon. Blood samples for measurement of cortisol were obtained at 90, 120, 150, 180, 210 and 240 min after glucagon injection. The lowest peak cortisol value of control cubjects (9.7 μg/dl) was considered as the cut-off value for adrenal insufficiency. Combination test was performed by injecting 1 μg of ACTH at the 180 min of GST and blood samples for cortisol measurement were obtained at 210 and 240 minutes. For the determination of optimal cut-off value for diagnosing adrenal insufficiency, Receiver Operating Characteristics (ROC) analysis was performed and 12.4 μg/dl of cortisol value was obtained with a sensitivity of 83% and specificity of 100%.

Results: Ten patients with adrenal insufficiency in both tests also had adrenal insufficiency in the combination test. Twenty-eight patients with normal cortisol response to both tests also had normal cortisol response to combination test. Two patients with adrenal insufficiency (peak cortisol responses were 13.4 and 13.1 μg/dl) at ACTH test and a patient with adrenal insufficiency at GST (peak cortisol response 8.7 μg/dl) had normal cortisol responses to combination test.

Conclusion: The combination test gave an additional information in three (7.3%) patients who had equivocal results in ACTH and glucagon tests. Moreover, by performing the combination test, we can save a day of the patients and evaluate GH axis concomitantly.