Central diabetes insipidus.

Central diabetes insipidus (CDI), characterized by polyuria and polydipsia, is caused by deficiency of arginine vasopressin (AVP), an antidiuretic hormone which acts on V2 receptors in kidney to promote reabsorption of free water. CDI is classified into three subtypes; idiopathic, secondary and familial. A previous study suggests that infundibulo-neurohypophysitis might be an underlying cause of idiopathic CDI. Among secondary CDI, the tumors in the central nervous system such as craniopharyngioma and germ cell tumors are the most frequent causes. Familial CDI is inherited mostly in an autosomal dominant mode, and the number of causal mutations in the AVP gene locus reported so far exceeds 80. CDI is treated with desmopressin, an analogue of vasopressin, and the tablet is preferred to the nasal form because it is easier to administer. It is also shown that the oral disintegrating tablet formula increases QOL and decreases the incidence of hyponatremia in CDI patients. In some CDI patients, the osmoreceptors in the hypothalamus do not function and patients do not sense thirst. These adipsic CDI patients are treated with desmopressin and adjusting the amount of daily water intake based on body weight measurement; but controlling the water balance is extremely difficult, and morbidity and mortality are shown to be high in these patients.