[The syndrome of inappropriate secretion of antidiuretic hormone in hypophyseal tumors].

70-year old man was admitted to the hospital due to the sudden change in his behaviour with the production of unusual echolalic word connections. Arginin-vasopressin (AVP) level (1.16 pg/ml) was found inappropriately higher in relation to the severe serum hypoosmolality (261 mmol/kg) and hyponatraemia (117 mmol/l) with relatively high urinary osmolality (590 mmol/kg) and natriuria (684 mmol/24 h). Diagnosis of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH-type C) was confirmed during the water load test. Magnetic resonance imaging and CT scans revealed in the region of hypophysis intrasellar tumour (diameter of 16 mm) and the stabilized finding of temporal cyst. Substitution of sodium losses with the restricted fluid intake resulted in the correction of water-electrolyte balance and the restoration of normal clinical state.