The Caveats of Corticotropin Stimulation Test in Diagnosing Secondary Adrenal Insufficiency: Case Reports and Literature Review

Corticotropin stimulation test (CST) is commonly used to diagnose secondary adrenal insufficiency. We present two patients who underwent transsphenoidal pituitary surgery for pituitary macroadenoma. Both patients had additional pituitary hormone deficiencies before and after the surgery. The patients were maintained on glucocorticoid (GC) replacement for at least 3 months after the surgery. In the remote follow-up period, they underwent conventional CST with resultant cortisol levels above 18 ug/dL. This led to discontinuation of GC treatment. Few months later, both patients developed clinically evident adrenal insufficiency. Providers should be cautious interpreting the results of CST in patients with pituitary disorders. The 250-ug CST with standard cortisol cutoff has low sensitivity and can give falsely reassuring results. Thus, it is prudent to use a higher cortisol threshold to define intact hypothalamic-pituitary-adrenal axis. J Endocrinol Metab. 2016;6(5):154-157 doi: http://dx.doi.org/10.14740/jem366w