SIADH - Syndrome of inappropriate ADH (SIADH) secretion is a disorder of fluid and electrolyte balance which results from the excessive release of antidiuretic hormone (ADH). This results in the inability to excrete dilute urine. SIADH is seen in association with certain cancers (e.g. oat cell lung cancer, pancreatic, prostate, Hodgkin's disease), central nervous system disorders, head injury, myxedema, psychosis, and certain drugs. The incidence is approximately 7 out of 100,000 people. Symptoms include weight gain, nausea, vomiting, muscle cramps, confusion, and convulsions.