Day 5 Morning Serum Cortisol Predicts Hypothalamic-Pituitary-Adrenal Function after Transsphenoidal Surgery for Pituitary Tumors

BACKGROUND: Adrenal insufficiency is a complication of transsphenoidal surgery (TSS) for pituitary ade-noma, and correct identification of patients requiring glucocorticoid replacement is important. Controversy exists over which early postoperative 9 AM cortisol con-centration reliably predicts hypothalamic-pituitary-adrenal (HPA) axis reserve, as defined by the insulin tol-erance test (ITT). METHODS: Data were reviewed for 36 patients undergo-ing TSS followed by day 5 postoperative 9 AM cortisol measurement and ITT 6 weeks postsurgery. All pa-tients received postoperative glucocorticoid replace-ment, which was discontinued if the 9 AM serum cor-tisol was300 nmol/L. RESULTS: Of 23 patients who failed the ITT (peak corti-sol 500 nmol/L), 20 also had a day 5, 9 AM serum cortisol300 nmol/L. Nine of 13 patients who passe