Diabetes insipidus (DI) is the most common disorder of the posterior lobe of the pituitary gland and is characterized by a deficiency of antidiuretic hormone (ADH) also called vasopressin.

Lack of ADH causes excessive thirst (polydipsia) and large volumes of dilute urine (polyuria), which characterize the disorder. It may occur secondary to head trauma, brain tumor, or surgical ablation or irradiation of the pituitary gland. It may also occur with infections of the central nervous system (meningitis, encephalitis, tuberculosis), conditions that increase intracranial pressure, surgery near to (or that causes edema to) the pituitary gland or hypothalamus, or with tumors (e.g., metastatic disease, lymphoma of the breast or lung). Manipulation of the pituitary gland during surgery may cause transient DI lasting several days. Another cause of DI is failure of the renal tubules to respond to ADH; this nephrogenic form may be related to hypokalemia, hypercalcemia, and a variety of medications (e.g., lithium, demeclocycline [Declomycin]).

The disease cannot be controlled by limiting fluid intake, because the high-volume loss of urine continues even without fluid replacement. Attempts to restrict fluids cause the patient to experience an insatiable craving for fluid and to develop hypernatremia and severe dehydration.

• Polyuria: enormous daily output of very dilute urine (specific gravity 1.001 to 1.005)
• Polydipsia: patient experiencing intense thirst, drinking 2 to 20 L of fluid daily, with a special craving for cold water
• Polyuria continuing even without fluid replacement
• In inherited DI, primary symptoms possibly beginning at birth; in adults, onset possibly insidious or abrupt

• Urine specific gravity
• Fluid deprivation test: fluids withheld for 8 to 12 hours until 3% to 5% of the body weight is lost; inability to increase specific gravity and osmolality of the urine during test characteristic of DI
• Other diagnostic procedures: concurrent measurements of plasma levels of ADH and plasma and urine osmolality and a trial of desmopressin (synthetic vasopressin) therapy and IV infusion of hypertonic saline solution

The objectives of therapy are (1) to replace ADH (which is usually a long-term therapeutic program), (2) to ensure adequate fluid replacement, and (3) to identify and correct the underlying intracranial pathology. Nephrogenic causes require different management approaches.

• Educate patient and family members about follow-up care, prevention of complications, and emergency measures.
• Provide specific verbal and written instructions, including the dose, actions, and adverse effects of all medications; demonstrate correct medication administration and observe return demonstrations. Educate the patient and family to recognize the signs and symptoms of hyponatremia.
• Advise patient to wear a medical identification bracelet and to carry medication information about this disorder at all times.

For more information, see Chapter 52 in Hinkle, J. L., & Cheever, K. H. (2018). Brunner and Suddarth's textbook of medical-surgical nursing (14th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.