The usefulness of combined biochemical tests in the diagnosis of Cushing's disease with negative pituitary magnetic resonance imaging

Objective: The etiological diagnosis of ACTH-dependent Cushing's syndrome is often a problem. In fact, no endocrine or radiological examination can conclusively distinguish the ectopic from the pituitary source of disease. The aim of our study was to evaluate the role of stimulation and suppression endocrine tests in the diagnostic and therapeutic approach of patients with Cushing's disease (CD) and negative pituitary magnetic resonance imaging (MRI), considering their post-surgical outcome in comparison with patients with CD and positive MRI. Patients and methods: We retrospectively analyzed 31 patients (25 women and 6 men, median age 40 ± 15 years) with a confirmed diagnosis of CD who underwent transsphenoidal pituitary surgery by the same neurosurgeon between 2001 and 2005. Preoperative endocrine assessment included corticotropin-releasing hormone (CRH), desmopressin (dDAVP), and overnight 8 mg dexamethasone suppression tests (8-DST) in all patients. Fifteen patients had a normal pi...