Ask An Expert: Diabetes Insipidus

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Ask An Expert: Diabetes Insipidus

Question:

Is diabetes insipidus related or similar to type 1 or type 2 diabetes?

Answer:

No, diabetes insipidus is not related to either type 1 diabetes mellitus or type 2 diabetes mellitus, although they all share the same "first name" and may have similar symptoms, including frequent urination and excessive thirst.

Both type 1 and type 2 diabetes mellitus have been called "sugar diabetes" because they involve insulin and control of blood sugar. In type 1 diabetes mellitus, (which used to be called juvenile diabetes), there is destruction of the insulin-producing cells of the pancreas, which leads to decreased production of insulin and abnormal handling of sugar by the body. In type 2 diabetes, (formerly called adult-onset diabetes), there is an abnormally high "resistance" to the effects of the insulin, which leads to high blood sugars.

Diabetes insipidus (DI) has nothing to do with insulin or blood sugar. It is a rare disorder caused by a decrease in secretion of a hormone called antidiuretic hormone (ADH), or an abnormally high resistance to the effects of the ADH hormone on the kidney. Without normal levels of ADH, the kidneys cannot properly control how much water is retained in the body and how much is lost in the urine. People with DI urinate very often and the urine is very dilute. They are also very thirsty, and can become dehydrated easily.

There are many causes of DI including damage to the pituitary gland in the brain, head injuries, cancers, eating disorders and psychiatric disorders. In about 30 percent of cases, however, no cause can be found.

Treatment depends in part on the cause of the diabetes insipidus. Sometimes people with DI can be treated with liquid solutions, either drinking them or getting them intravenously, to replace lost fluids and avoid dehydration. Medication, including a synthetic version of the ADH hormone known as DDAVP, may be required. One type of DI does not respond to synthetic hormone, and medications such as hydrochlorothiazide (HCTZ) or Moduretic are used instead. It is important that all people with diabetes insipidus wear a medical-alert bracelet or carry a wallet card to help make sure they are always given proper treatment.

Diana Post, M.D., is an assistant professor of medicine at Harvard Medical School and a member of the Department of Medicine at Brigham and Women's Hospital.

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Last updated:	January 24, 2007