Patients with low levels of ACTH and Cushing's syndrome will undergo routine tests to confirm that they have hypercortisolism, low ACTH, and adenoma or MMAD on CT scans. They will fill out a questionnaire about quality of life. They will also undergo 3-7 days of research testing with a variety of agents to investigate whether these agents increase cortisol. Following this, patients will be scheduled for adrenalectomy at the NIH. This is the standard treatment for these conditions. The abnormal tissue obtained at surgery will be used for laboratory studies to evaluate whether the same or other agents may be the cause of excess cortisol production.