New Imaging Techniques in the Evaluation of Patients With Ectopic Cushing Syndrome

Cushing Syndrome is an endocrine disorder causing an over production of the hormone cortisol. Cortisol is produced in the adrenal gland as a response to the production of corticotropin (ACTH) in the pituitary gland. Between 10% and 20% of patients with hypercortisolism (Cushing Syndrome) have ectopic production of the hormone ACTH. Meaning, the hormone is not being released from the normal site, the pituitary gland. In many cases the ectopic ACTH is being produced by a tumor of the lung, thymus, or pancreas. However, in approximately 50% of these patients the source of the ACTH cannot be found even with the use of extensive imaging studies such as computed tomography (CT) scans, magnetic resonance imaging (MRI), and nuclear scans (111-indium pentetreotide). The ability of these tests to locate the source of the hormone production is dependent on the changes of anatomy and / or the dose and adequate uptake of the radioactive agent. The inability to detect the source of ectopic ACTH production often results in unnecessary pituitary surgery or irradiation. Unlike the previously described tests, positron emission tomography (PET scan) has the ability to detect pathologic tissue based on physiologic and biochemical processes within the abnormal tissue. This study will test whether fluorine-18-fluorodeoxyglucose (FDG), fluorine-18-dihydroxyphenylalanine (F-DOPA) or use of a higher dose of 111-indium pentetreotide can be used to successfully localize the source of ectopic ACTH production.