pathological endocrine condition characterized by excessive thirst and excessive production of very dilute urine. The disorder is caused by a lack of antidiuretic hormone (vasopressin) or a blocking of its action. This hormone, produced by the hypothalamus, regulates the kidney's conservation of water and production of urine through its ability to stimulate reabsorption of water by the kidneys.

The causes may be numerous: failure of osmoreceptors (receptors in the hypothalamus that sense variation in osmotic pressure of body fluids); tumours; inflammation of the hypothalamus or posterior pituitary lobe (neurohypophysis) by such diseases as meningitis; granulomas; trauma, such as skull fracture or concussion; or failure of the tubules to respond to antidiuretic hormone.

The form of the disorder that results from injury to the hypothalamic nucleus, which is the tract by which vasopressin is conveyed to the neurohypophysis for storage, is called central diabetes insipidus (CDI). Nephrogenic diabetes insipidus (NDI) results when the supplies of vasopressin are adequate but the kidney tubules are unresponsive—either genetically or because of potassium depletion, high levels of serum calcium, treatment with lithium, or other disorders. Central diabetes insipidus can be alleviated by injections of vasopressin of synthetic origin; such treatment, however, is ineffective for NDI.