Diabetes Insipidus
What is it?
Diabetes insipidus, not to be confused with the more common diabetes mellitus, is a relatively rare disorder resulting from a failure to produce sufficient amounts of vasopressin, also known as antidiuretic hormone (ADH). Vasopressin, produced by the hypothalamus and secreted by the posterior pituitary gland, helps the kidneys to reabsorb water and maintain proper fluid balance. If the pituitary fails to produce enough ADH, water is not conserved but simply passed through the kidneys and excreted, typically in very large quantities. More rarely, the kidneys fail to respond properly to ADH; this is known as nephrogenic diabetes insipidus. Dehydration is the primary health risk associated with either form. Diabetes insipidus affects both sexes equally. With proper treatment, overall prognosis is good (except in cases caused by cancer).
What Causes It?
- In approximately one third of all cases, the cause of diabetes insipidus is unknown.
- Hereditary factors may play a role in some cases.
- Damage to the pituitary gland from a head injury, a hypothalmic tumor, or inflammation, radiation therapy, or surgery may lead to diabetes insipidus.
- The most frequent cause of nephrogenic diabetes insipidus is therapy with lithium.
Prevention
- There is no known way to prevent diabetes insipidus.
Diagnosis
- Physical examination and patient history are needed. Diagnosis of diabetes insipidus is suspected when a patient reports unusually large and frequent urine output.
- A urinalysis is done to discover dilute urine (low specific gravity).
- A water deprivation test may be conducted. The patient consumes no fluids for eight hours while urine output and specific gravity are monitored. Patients with diabetes insipidus continue to produce large amounts of urine despite dehydration. An injection of vasopressin reduces urine volume and produces a concentrated urine in those with pituitary diabetes insipidus (but not nephrogenic diabetes insipidus).
- Blood tests may be taken to assess water and salt balance.
How to Treat It
- Vasopressin (synthetic ADH) may be administered (either in a nasal spray, as a pill, or by injection) to replace or supplement the body's ADH production. Such hormone therapy is usually necessary for a lifetime, although if diabetes insipidusis caused by a head injury or surgery, it may be possible to discontinue treatment.
- To treat nephrogenic diabetes insipidus, your doctor may advise a low-salt diet to reduce thirst and slow the excretion of water. Certain diuretics may also be prescribed. (Nephrogenic diabetes insipidus does not respond to ADH treatment.)
- Drink plenty of fluids to prevent dehydration.
- Consume plenty of high-fiber foods and fruit juices to prevent or treat constipation.
When to Call a Doctor
- See a doctor immediately if you develop symptoms of diabetes insipidus.
- EMERGENCY Call an ambulance if you observe someone lose consciousness.
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Copyright © 2008 Medletter Associates, LLC
Content excerpted from Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference.