Participants will undergo 3 to 7 days of testing to determine if their cortisol level rises after taking certain medicines or eating certain foods. These foods and medicines, chosen to mimic or stimulate substances already in the body, are: glucagon, ACTH, gonadotropin-releasing hormone, vasopressin, thyrotropin-releasing hormone, and a mixed meal consisting of a protein, carbohydrate and fat (usually chicken breast and a milkshake-like drink). Blood will be collected at intervals before and after taking the food or medicine to measure cortisol blood levels. Blood will also be collected while the patient is in a standing position and while lying in bed, because changes in posture can cause substances in the body to increase or decrease. Depending on the individual's response to these tests, additional tests may be done with insulin, glucose, luteinizing hormone and follicle-stimulating hormone.