[Endocrinological analysis of chronic hypernatremia in two cases of hydranencephaly].

We reported two infants with hydranencephaly and chronic hypernatremia. Their plasma sodium concentration gradually increased during the first week and remained between 150-160 mEq/L thereafter. They showed no signs of thirst. A water deprivation test demonstrated low urine osmolality and low plasma ADH concentration despite markedly elevated plasma osmolality in both cases. Urine was significantly concentrated when vasopressin was given. Thus, it was concluded that both thirst mechanism and ADH secretion were disturbed in these two cases. ADH producing cells, the thirst center and the osmoreceptor are all located in the hypothalamus. Radiographic measures showed dysplasia of the hypothalamus, providing the anatomical basis for their dysfunction.