Mifepristone Dynamic Testing for Diagnosis for Central Adrenal Insufficiency

Inclusion Criteria (1 of the following): * Completed insulin tolerance testing (ITT) at University of Michigan from 2012 to present. * Are scheduled to complete ITT. * Are clinically suspected to have adrenal insufficiency but have not undergone ITT. Exclusion Criteria: * Female patients who are of child-bearing potential (defined as a sexually mature woman who has not undergone hysterectomy, bilateral oophorectomy bilateral salpingectomy or bilateral tubal ligation/occlusion, at least 12 weeks prior to screening, or who has not been naturally postmenopausal for at least 24 consecutive months prior to study enrollment) and not using non-hormonal contraception. * Female patients not willing to use non-hormonal contraception for one month following treatment. * Women who are pregnant or breast feeding. * Patients with an existing diagnosis of adrenal insufficiency who are on any glucocorticoid replacement other than oral hydrocortisone or prednisone. * Patients on medications that are strong CYP3A * Patients taking other medications metabolized by CYP3A * Patients who have a history of QT prolongation and patients with any recent abnormal electrocardiogram (ECG).