Thirst, resetting of the osmostat, and water intoxication following encephalitis.

A young man developed pathological thirst and hyperdipsia, hyperphagia, disordered temperature regulation, a lowered threshold for aggressive behavior, apathy, impaired memory, and seizures following encephalitis. He had marked hyponatremia. Bouts of water drinking produced water intoxication and precipitated status epilepticus. Studies of water handling with measurements of plasma osmolality and arginine vasopressin (AVP) revealed a very low thirst threshold (below 242 mOsm/kg) with resetting of the osmostat to a new level (255 mOsm/kg) but normal control of plasma osmolality at that level with adequate AVP release.