Ectopic atrial natriuretic peptide production in small cell lung cancer with the syndrome of inappropriate antidiuretic hormone secretion.

One autopsy case with small cell lung cancer and the syndrome of inappropriate antidiuretic hormone secretion (SIADH) is reported. Both plasma atrial natriuretic peptide (ANP) and arginine vasopressin (AVP) levels were high, and the presence of significantly high levels of ANP and AVP in tumor tissue was confirmed by gel chromatography and radioimmunoassay techniques. To the best of the authors' knowledge, this is the first case in which ectopic ANP production and its secretion into blood (leading to SIADH) were proved.