Improved methods and systems for diagnosing and for treating Cushing's syndrome and Cushing's Disease are provided herein, including methods and systems for concurrently treating Cushing's syndrome and differentially diagnosing Cushing's Disease from Ectopic Cushing's Syndrome in a patient with an established diagnosis of ACTH-dependent Cushing's syndrome. Treatment methods can use glucocorticoid receptor antagonists (GRAs), which differentially affect the ratio of cortisol to ACTH levels in patients having Cushing's Disease versus patients having Ectopic Cushing's Syndrome. Methods for concurrently treating and differentially diagnosing Cushing's Disease from Ectopic Cushing's Syndrome include obtaining baseline cortisol and ACTH levels of a patient, treating the patient with a GRA according to a protocol that would typically substantially elevate cortisol levels, obtaining post-treatment cortisol and ACTH levels of the patient, determining a differential relationship between baseline cortisol and ACTH levels and post-treatment cortisol and ACTH levels and providing a positive diagnosis based on the differential relationship.
