Psychogenic polydipsia

MYTH: Diabetes insipidus (DI) is a syndrome characterized by excessive glucose in the urine.

FACT: Diabetes insipidus is characterized by production of abnormally large volumes of dilute urine. A 24-hour urine output greater than 50 ml/kg is characteristic.

MYTH: Diabetes insipidus is caused by an actual or relative deficiency of insulin.

FACT: The three main types of diabetes insipidus-pituitary, nephrogenic, and primary polydipsia-are all related to antidiuretic hormone (ADH), not insulin. Decreased secretion or decreased action of ADH prevents the hormone from acting on the renal tubules to retain water and concentrate urine.

MYTH: Only a few conditions can precipitate DI.

FACT: Many conditions can cause DI, but common ones include trauma to the brain or head (pituitary DI), drugs such as lithium (nephrogenic DI), and psychogenic disorders or disorders associated with abnormal thirst (primary polydipsia).

MYTH: Diabetes insipidus is relatively benign.

FACT: Untreated DI can lead to death from electrolyte imbalances, dehydration, hemodynamic instability, central nervous system depression, and circulatory collapse.

MYTH: Medical management of DI includes fluid and electrolyte replacement, plus dexamethasone.

FACT: Medical management depends on the type of DI. For example, patients with pituitary DI may be treated with desmopressin, which increases urine concentration and decreases urine output. Patients with nephrogenic DI are treated with thiazide diuretics (with or without amiloride) and a low-sodium diet. Primary polydipsia is usually corrected with patient counseling.

MYTH: Vasopressin is the drug of choice in patients needing long-term treatment for pituitary DI.

FACT: Although vasopressin injection may be used in emergency treatment of DI, it's not practical for longterm therapy because of its short duration of action. Intranasal desmopressin has a longer duration of action and fewer adverse effects, so many experts consider it the drug of choice for long-term treatment of pituitary DI.

BY EDWINA A. McCONNELL, RN, PHD, FRCNA

At the time this article was written, Edwina A. McConnell was an independent nurse-- consultant in Gorham, Me. Selected references for this article are available on request

Copyright Springhouse Corporation Jun 2003
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