Effects of Hormone Stimulation on Brain Scans for Cushing s Disease

Background: * Cushing s disease can be caused by a tumor of the pituitary gland, a small gland about the size of a pea located at the base of the brain. These tumors produce high levels of hormones, which cause obesity, diabetes, and growth problems. The cure for this type of Cushing s disease is to have surgery that removes the tumor but leaves the pituitary gland alone. Currently, magnetic resonance imaging scans are the best way to find these tumors. However, many of these tumors do not show up on the scan. * Positron emission tomography (PET) scans use radioactive chemicals to light up parts of the body that are more active, such as tumors. Researchers want to try to make the small Cushing s disease tumors more active to help them show up on the scans. A special hormone will be given before the scan to make the tumors more active. Objectives: - To test the use of hormone stimulation to improve brain scans for Cushing s disease tumors. Eligibility: - Individuals at least 8 years of age who will be having surgery to remove Cushing s disease tumors. Design: * Participants will be screened with a medical history, physical exam, blood and urine tests, and imaging studies. * They will have three brain scans before surgery. The first scan is a magnetic resonance imaging scan to show a full picture of the brain. The second and third scans are PET scans. * The first PET scan will be given without the special hormone. The second PET scan will be done more than 24 hours but less than 14 days after the first PET scan. The second PET scan will be given with the special hormone. * Participants will have tumor removal surgery through another study protocol.