[Repeated serious water intoxication in an aged patient. (Data on the relationship between the inappropriate antidiuretic hormone syndrome and the atrial natriuretic factor)].

An old women was in an 8-year-period 9 times admitted to the hospital because of severe mental disturbances. The average serum sodium concentration was 126.25 +/- 2.43 mmol/l at the admissions; it increased to 139.44 +/- 1.40 mmol/l after intravenous infusion of hypertonic solutions accompanied with the disappearance of the mental disturbances. The patient was usually chronically hyponatremic due to the increased water intake and the insufficient water excretion. The latter was induced by the augmented vasopressin levels. The remarkable feature of the syndrome of inappropriate antidiuretic hormone secretion was its association with lowered blood level of atrial natriuretic factor accompanied by sodium, and volume depletion. Discontinuation of the exaggerated water intake resulted in the elimination of the permanent hyponatremia; no episode of water intoxication occurred during the last 3 and 1/2 years.