ASSESSING THE HYPOTHALAMO-PITUITARY-ADRENAL AXIS IN PATIENTS ON LONG-TERM GLUCOCORTICOID THERAPY - THE SHORT SYNACTHEN VERSUS THE INSULIN TOLERANCE-TEST

The short synacthen test (SST) is an effective method of assessing the hypothalamo-pituitary-adrenal (HPA) axis in patients with pituitary d isease. Chronic glucocorticoid therapy may result in suppression of th e HPA axis, and use of the SST has not been evaluated in these patient s. This study compares the SST with the insulin tolerance test (ITT) i n patients on long-term corticosteroid therapy. Both tests were done o n 22 patients on long-term, stable-dose prednisolone (<10 mg/day). A p ass was defined as a 30 minute plasma cortisol >550 nmol/l for the SST and a maximal cortisol of >500 nmol/l for the ITT. Five patients pass ed both tests; nine failed both. Eight patients had discrepant results ; all passed the ITT but failed the SST. There was a significant corre lation (p<0.001) between the maximum cortisol level achieved during th e ITT and the 30 min SST value and the incremental rise. There was an inverse correlation between the dose and duration of use of steroids a nd the cortisol response during both tests. The SST is a reliable, saf e and easily performed initial assessment of the HPA axis in patients on long-term corticosteroids. The ITT remains a valuable test for thos e who fail the SST.