Introduction: The study aim was to compare serial Short Synacthen test (SST) results to diagnose secondary Adrenal Insufficiency (AI) in patients with confirmed pituitary diseases.
Methods: Serial SST results of patients, tested between 2006 and 2018 in the department of Diabetes and Endocrinology, at a tertiary centre, were reviewed retrospectively. Patient details were obtained from local dynamic test database, maintained by Endocrine Nurse Specialist. SST results were included only if patients had pituitary disease and underwent SST more than once. Details of surgical and radiotherapy interventions were obtained. Assay specific cut-offs were applied and appropriate cortisol responses recorded at 30 and 60 min. Results were interpreted as pass if either 30 min or 60 min or both values were above cut-off excluding secondary AI. Results were paired with baseline and final values based on either 30 min only or combined 30 and 60 min SST results to diagnose failure of HPA axis.
Results: A total of 118 patients underwent 465 SSTs (mean 3.94 tests / patient). There were 60 males and 58 females. Fifty one patients underwent Pituitary surgery and 52 received Radiotherapy. At baseline, 78/118 (66%) patients passed the test which included 15/118 (12%) patients showing suboptimal response (failed) at 30 min and satisfactory response (passed) at 60 min. On final assessment, 87/118 (73%) patients showed intact HPA axis both at 30 and or 60 min, while 31/118 (26%) failed the test with suboptimal response at 30 and 60 min. Out of 87/118 patients who passed the test, 11/118 (9%) would have been started on corticosteroid therapy, if only 30 min values were used.
Conclusion: The study suggests that measuring both 30 and 60 min cortisol levels during SSTs can avoid initiation of corticosteroid replacement therapy in some patients. Further large scale studies are needed to validate our findings.