Clinical Usefulness of Corticotropin Releasing Hormone Testing in Subclinical Cushing's Syndrome for Predicting Cortisol Replacement after Adrenalectomy

PURPOSE: The purpose of this study was to investigate the clinical and hormonal features of patients with incidentally discovered adrenal adenomas in relation to corticotropin releasing hormone (CRH) testing and the clinical outcome of adrenalectomy. MATERIALS AND METHODS: Twenty-three consecutive patients with incidentally detected adrenal adenomas were included in this retrospective study. All the patients underwent abdominal computed tomography scans and hormonal assays, including assessment of circadian rhythms of plasma cortisol and corticotropin (adrenocorticotropic hormone, ACTH), a corticotropin stimulation test, and low-dose and high-dose dexamethasone tests. The patients were reevaluated at regular intervals (6, 12, and 24 months) for a median period of 24 months. Subclinical Cushing's syndrome (SCS) was diagnosed in patients with subtle hypercortisolism who did not present clinical signs of Cushing's syndrome. RESULTS: We calculated the responsive index (peak value of ACTH in CRH test/baseline value of ACTH in CRH test). Of 23 patients, 6 had Cushing's syndrome, 8 had SCS, and 9 had a non-functioning tumor. All patients underwent laparoscopic adrenalectomy. Several patients (5 of 6 with Cushing's syndrome and 2 of 8 with SCS) required cortisol replacement therapy after surgery. The remaining patients required no hormonal replacement after surgery. Those who required hormone replacement had a responsive index of less than 1.2. Those who did not need hormone replacement therapy had a responsive index of more than 2.0. CONCLUSIONS: In our limited experience, the responsive index of the CRH test might be a valuable tool for predicting the need for cortisol replacement after surgery in patients with SCS.