Endocrine Abstracts

Introduction: Insulin tolerance test (ITT) is considered as the gold standard assessment for hypothalamic–pituitary–adrenal axis (HPA) integrity. Short synacthen test (SST) is a relatively simple, low-cost and well tolerated first line test of HPA despite concerns regarding accuracy. The glucagon stimulation test (GST) is often used as an alternative to the ITT. Although less reliable, it is particularly useful when insulin-induced hypoglycaemia is contra-indicated. This retrospective audit set to evaluate accuracy of the SST and GST against the ITT with the aim of advising on the best method of HPA investigation.

Method: Patients who underwent ITT between 2009 and 2012 and had at least one screening test were audited. The ITT was considered as gold standard and pre-screening SST and/or GST results were compared against it.

Results: patients underwent ITT of whom 31 had pre-screening SST and/or GST. 21 were females and average age was 42.9. 23 with clinically suspected hypopituitarism; six post-transphenoidal surgery and two with none ACTH-producing pituitary adenoma. 26 of the 31 patients underwent both SST and ITT. 13 patients failed both SST and ITT and only one patient passed SST but failed ITT giving an SST sensitivity of 92.8% (95% CI 86.1–99%) and a specificity of 8.3% (95% CI 4–16.2%). Six out of 16 patients underwent both GST and ITT failed both tests, while two passed GST but failed ITT giving GST sensitivity of 75% (95% CI 75–94.7%) and a specificity of 0% (95% CI 0–19.7%). Measure of agreement between SST and GST was poor (κ=−0.13).

Conclusion: SST is more sensitive and specific than GST for assessing HPA when compared to the gold standard ITT.

Recommendation: SST is a more appropriate screening test for HPA axis and should replace the GST when ITT is contraindicated.