Endocrine Abstracts

Introduction: The 1 μg low dose short Synacthen tests (LDSST) and the glucagon stimulation tests (GST) have been suggested to be safer alternatives to the insulin induced hypoglycaemia stress test. The aim of this study was to compare the peak plasma cortisol concentration in response to a LDSST followed 60 min later by a GST in children undergoing investigation for short stature.

Methods: We retrospectively studied 38 patients (19 female, 19 male) who underwent evaluation for short stature between May 2006 and January 2010. Their mean age was 11.08 years and median age was 11.1 (range 1.99–18.10 years). An intravenous LDSST was followed by an intramuscular GST. Blood samples were drawn at 0, 20 and 30 min for the LDSST and 0, 30, 60, 90, 120, 150 and 180 min for the GST.

Results: From the 38 tests, four children in the LDSST and 17 in the GST group had a peak cortisol <500 nmol/l. Three children had a peak cortisol <500 nmol/l with both the LDSST and the GST. There was a biased relationship between the two tests with LDSST giving higher results at lower and GST at higher concentrations. Passing & Bablock shows that GST=(1.91×SST)−607.

Discussion: The difference in peak cortisol concentrations may be due to the different pharmacological mechanisms that Synacthen and glucagon employ. The skewed distribution of responses would suggest that the difference is not due to the order in which the tests were performed. Our study would suggest that common cut-off values cannot be used for different secretagogues.