diabetes insipidus

diabetes insipidus [in sip′i dəs]

n.

〚ModL, lit., insipid diabetes〛

a disorder caused by a pituitary deficiency and characterized by the heavy discharge of urine and intense thirst

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Endocrine disorder causing extreme thirst and excessive production of very dilute urine, apparently due to lack of antidiuretic hormone (vasopressin, which regulates the kidney's water conservation and urine production) or failure of the kidney tubules to respond to it.

Injections of synthetic vasopressin are effective if the hormone is lacking but not if the response is absent. Disorders of the hypothalamus are one cause of diabetes insipidus.

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▪ medical disorder

      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.

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