Hypodipsic hypernatremia with intact AVP response to non-osmotic stimuli induced by hypothalamic tumor: A case report

Anatomical lesions of hypothalamic area associated with hypodipsic hypernatremia have been reported only rarely. We report here a case of hypodipsic hypernatremia induced by a hypothalamic lesion. A 25-yr-old man, who had been treated with radiation for hypothalamic tumor 5-yr before, was admitted for evaluation of hypernatremia and hypokalemia. He never felt thirst despite the elevated plasma osmolality and usually refused to drink intentionally. Plasma arginine vasopressin (AVP) level was normal despite the severe hypernatremic hyperosmolar state and urine was not properly concentrated, while AVP secretion was rapidly induced by water deprivation and urine osmolality also progressively increased to the near maximum concentration range. All of these findings were consistent with an isolated defect in osmoregulation of thirst, which was considered as the cause of chronic hypernatremia in the patient without an absolute deficiency in AVP secretion. Hypokalemia could be induced by activation of the renin-angiotensin-aldosterone system as a result of volume depletion. However, inappropriately low values of plasma aldosterone levels despite high plasma renin activity could not induce symptomatic hypokalemia and metabolic alkalosis. The relatively low serum aldosterone levels compared with high plasma renin activity might result from hypernatremia. Hypernatremia and hypokalemia were gradually corrected by intentional water intake only.

A case of hypodipsic hypernatremia

Hypodipsic hypernatremia is characterized by chronic or recurrent episodes of severe hypernatermia associated with dehydration and a lack of thirst. This constellation of deficits suggests that the syndrome is due to hypodipsia of destruction of the hypothalamic osmoreceptors that regulate thirst and ADH secretion. We report a child with abnormalities of the central nervous system who had hypernatremia and a lack of thirst without detectable abnormalities in the osmoregulation of ADH secretion. The patient was a 11 month old female and her chief complaints were poor oral intake and weight gain. There were recurrent hypernatremia with hyperosmosis and normal level of plasma ADH. With intravenous rehydratin, oral intake was improved and plasma sodium level decreased.