Usefulness of FDG-PET in detecting an ADH-secreting tumor: a case report.

We report a case of a 41-year-old woman who was diagnosed as having the syndrome of inappropriate secretion of ADH (SIADH). There was no evidence of any disorders of the central nervous system, lung diseases, or drugs causing SIADH. Positron emission tomography (PET) using (18)F-fluorodeoxyglucose (FDG) was performed and indicated a tumor of the uterine cervix. After resection of the tumor, both serum sodium level and serum osmolarity were normalized concomitantly with a decrease in serum ADH level. This is the first case report suggesting the usefulness of a FDG-PET scan to detect an occult cancer responsible for SIADH. It seems plausible that FDG-PET may be helpful in the diagnosis of other ectopic hormone-producing tumors such as ectopic ACTH-producing tumors that cause Cushing's syndrome.