Prognostic usefulness of ACTH in the postoperative period of Cushing's disease.

Objectives: To analyze the usefulness of plasma ACTH in predicting CD remission after surgery and to evaluate the prognostic usefulness of ACTH measurement after the cortisol and ACTH nadir (48 h prior to discharge). Design: A prospective study was made of 65 patients with CD operated upon between 2005 and 2016. Methods: Postsurgery plasma ACTH and cortisol were measured every 6 h, in the absence of corticosteroid coverage. Hydrocortisone was started in the presence of adrenal insufficiency or cortisol <55.2 nmol/L. Plasma ACTH was again determined before discharge. Main outcome measure: Usefulness of plasma ACTH in predicting CD remission. Results: Remission at 3 months of CD was achieved in 56 of 65 cases, with late recurrence in 18 of 58 cases. Following resection, the ACTH nadir was significantly lower referred to late remission (2.8 vs 6.5 pmol/L; P = 0.031) and higher for recurrence (2.1 vs 4.8 pmol/L; P <0.001), and identical results were obtained for the ACTH values before discharge. In the analysis of the ROC curves, nadir and before discharge ACTH values <1.9 pmol/L and <2.6 pmol/L were respectively indicative of early remission (AUC 0.827; P <0.001); <6.2 pmol/L of remission at 3 months (AUC 0.847; P = 0.001) and >3.2 pmol/L of recurrence (AUC 0.810; P <0.001) in both ACTH values. A time to ACTH nadir <46 h was indicative of early remission (AUC 0.751; P = 0.001), while a time >39 h was indicative of recurrence (AUC 0.773; P = 0.001). Conclusions: We propose an ACTH value <3.3 pmol/L as a good long-term prognostic marker in the postoperative period of CD. Reaching the ACTH nadir in less time is associated to a lesser recurrence rate.