Postoperative day 1 versus postoperative day 5 morning cortisol for predicting an intact hypothalamic-pituitary axis: A cohort analysis

BACKGROUND: A reliable standard for evaluating postoperative hypothalamic-pituitary-axis (HPA) function following transsphenoidal pituitary surgery (TSS) could reduce hospital stays and unnecessary prolonged steroid therapy. We retrospectively examined the predictive role of morning cortisol levels on long-term HPA function to develop an institutional protocol. Here, we report the results of this analysis, which is the first to report the predictive strength of multiple variables (i.e., timing of measurement and values of serum cortisol cutoffs) within the same cohort. METHODS: A retrospective chart review was performed in 183 patients at a single institution from 2007 to 2012. 67 patients met inclusion criteria. The predictive value of postoperative day (POD) 1 and POD 5 morning cortisol for HPA function as determined by 1 ug cosyntropin stimulation test was evaluated using standard confusion matrix calculations and receiver-operator control curve analysis. RESULTS: In our cohort, an early POD 5 serum morning cortisol ≥15 ug/dl predicted an intact HPA axis with 100% specificity, 51% sensitivity, and a positive predictive value (PPV) of 100%. A POD 1 serum cortisol ≥25 ug/dl was needed to achieve a specificity of 100% and PPV of 100% to predict an intact HPA axis with a sensitivity of 30%. A POD 1 serum cortisol ≥18 ug/dl predicted an intact HPA axis with 33.3% specificity, PPV of 90.9%, and a sensitivity of 51.3%. CONCLUSION: A POD 5 morning cortisol level ≥15 ug/dl is an excellent predictor of normal postoperative HPA function in patients undergoing TSS for pituitary adenoma.