<prompt> The syndrome of inappropriate antidiuretic hormone is characterized by the following:Hyponatremia and hyperkalemiaHypernatremia and hypokalemiaHyponatremia and urine sodium excretion 20 meq1Hypernatremia and urine sodium excretion20 meq1  <response>: Syndrome of inappropriate antidiuretic hormone is caused by excess secretion of vasopressin leading to increased absorption of water resulting in hyponatremia, inappropriate sodium secretion in the urine 20 mEqL, hyper osmolar urine 100mOsmL and hypo osmolar plasma 260mOsmL. Ref: The MD Anderson Manual of Medical Oncology, 2nd Edition, CHAPTER 46 