Patients from a tertiary endocrine center at a University Hospital in Munich, Germany, were tested using Metyrapone (Metopirone®, HRA Pharma, France), administered at a dose of 40 mg/kg bodyweight at 8 a.m. Levels of ACTH were determined at 0, 60, 120, 180, and 240 minutes. Patients were categorized according to their need of glucocorticoid substitution at the end of follow-up. The study was approved by the local Ethics Committee with a limitation to 25 patients.