[Partial defect in the secretion of antidiuretic hormone and disproportionate polydipsia (author's transl)].

A 20-year-old patient was evaluated because of polydipsia and polyuria; by means of the dehydration test a partial defect in the secretion of antidiuretic hormone (ADH) was demonstrated, since the urinary osmolality after the administration of exogenous vasopressin was superior by 25 percent to the maximum spontaneous urinary osmolality reached after a period of fluid restriction. Nevertheless, there was also a component of psychogenic polydipsia because the daily basal fluid intake was superior to 15 liters, and in view of the fact that the urinary osmolality could reach 600 mOsm/kg, the endocrine defect cannot totally be responsible for the enormous volume of fluid intake. This is the first case in the world literature in which the association between potomania and deficiency in the secretion of ADH is reported. Since ADH is one of the factors which regulate the behaviour of various animal species it is possible that its deficiency may be directly responsible for the psychic disorder which led to the potomania. It is also possible that an anatomical hypothalamic lesion, too small to be demonstrated, might have a simultaneous effect on the centers regulating thirst and the neurons producing vasopressin.