The syndrome of inappropriate antidiuretic hormone is characterized by the following:

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 mEq/L), hyper osmolar urine (>100mOsm/L) and hypo osmolar plasma (<260mOsm/L). Ref: The MD Anderson Manual of Medical Oncology, 2nd Edition, CHAPTER 46