[Acquired disorder of thirst perception with intact osmoregulation of vasopressin]

We report a 45 y old male patient with severe hypodipsia, but intact vasopressin secretion and maximal renal response to vasopressin. The patient presented during hot summer days, 18 months after a frontal lobe hemorrhage due to a ruptured aneurysm, with severe hypernatremia (171 mmol/L) and a plasma osmolality of 348 mosm/kg. He was awake and had no interest in fluid intake. After initial correction, a thirst test for 36 hours was performed. Plasma osmolality rose from 295 to 320, urine osmolality rose from 220 to 700 mosm/kg, while plasma vasopressin levels increased more than 3-fold. Throughout the test the patient did not exhibit appreciable thirst. The intact osmoregulation of vasopressin as evidenced by the plasma levels and the elicited renal response, indicates that a selective acquired disturbance of thirst is present. Whether the thirst center is destroyed or/and thirst recognition (frontal lobe affection) is disturbed primarily, can not be decided.