Adenocarcinoma of the prostate with ectopic antidiuretic hormone production: a case report.

An 88-year-old patient with a poorly differentiated adenocarcinoma of the prostate gland was found to have all cardinal findings of syndrome of inappropriate antidiuretic hormone secretion (SIADH). Elevated levels of antidiuretic hormone were found in the patient's serum and in the prostatic tumor and the cytoplasms of the tumor was positive for prostate specific antigen and was faintly positive for antidiuretic hormone (ADH). He responded well to combination therapy of androgen blockade with leuprorelin acetate and flutamide, and laboratory findings of SIADH and serum ADH level returned to normal. However, he died of sudden profuse bleeding caused by gastric ulcers 6 months after the therapy. Ten cases of SIADH caused by prostatic cancer have been reported including the present case.