In patients receiving nivolumab, hyponatremia can be attributed to hypovolemia, syndrome of inappropriate ADH secretion, or endocrinopathies related to ICIs, such as hypophysitis, primary adrenal insufficiency, and hypothyroidism.31,32 Hyponatremia, regardless of its causes, should be recognized as an important warning sign of poor outcomes in patients with cancer. This evidence concerns the gene AVP and Hypovolemia.