Diabetes insipidus is a rare condition that can result in a fluid imbalance in the body. Although the name is similar, the condition has no relation to diabetes mellitus, which affects blood sugar. Diabetes insipidus is not curable; however, there are treatments available to help normalize fluid intake and output.
Definition & Facts
Diabetes insipidus occurs when the body does not produce enough antidiuretic hormone (also known as vasopressin) or the kidneys fail to respond to the hormone. In order for the body to maintain the proper balance and composition of fluids, a small gland called the hypothalamus produces antidiuretic hormone (ADH)/vasopressin. This hormone is stored in the pituitary and released as needed to regulate thirst and urination. When the hormone reaches receptors in the kidneys, it tells them to make less urine in order to keep more fluid in the body.
There are four types of diabetes insipidus. Central diabetes insipidus, which is caused by damage to the pituitary gland, is the most common form of the disease. Nephrogenic diabetes insipidus occurs when the kidneys are not able to respond to the ADH released by the pituitary. Dipsogenic diabetes insipidus is the result of a defect in the thirst mechanism, which is controlled by the hypothalamus. Gestational diabetes insipidus occurs during pregnancy when a specific placenta enzyme destroys the mother’s ADH.
Symptoms & Complaints
While a healthy adult may produce about three quarts of urine a day, a person with diabetes insipidus may produce as much as 16 quarts of dilute, pale urine in a single day. This can significantly impact the individual’s normal daily activities and interfere with sleep because of frequent nighttime urination and bedwetting.
In extreme cases, a person with diabetes insipidus may become severely dehydrated. When this occurs, the individuals will have dry lips and mucous membranes, sunken eyes, high grade fever, muscle spasms, lethargy, and increased irritability or confusion.
The cause of diabetes insipidus varies depending on the type of the disease. With central diabetes insipidus, the pituitary or hypothalamus is damaged. The damage is usually the result of surgery, tumor, inflammation, illness, or a traumatic head injury. Medications, such as lithium or certain antiviral drugs, can damage the kidney tubules that control the reabsorption and excretion of water so that they no longer respond to ADH.
An inherited genetic defect can also cause diabetes insipidus in children. Damage to the hypothalamus, prolonged intake of excessive fluids, and even certain types of mental disorders can lead to dipsogenic diabetes insipidus. Over time, the excessive intake of fluids suppresses the production of ADH and damages the kidneys so that they are unable to concentrate urine. Some cases of diabetes insipidus are idiopathic, which means that the underlying cause cannot be determined.
Diagnosis and Tests
Some of the symptoms of diabetes insipidus are similar to other conditions, including diabetes mellitus, so a variety of tests are required to confirm the diagnosis. The doctor may perform a supervised water deprivation test. During the test, the patient is advised not to drink fluids for a specific amount of time. The doctor monitors and measures changes in body weight, urine output, and urine concentration during the time that the fluids are withheld.
Blood tests may also be used to measure concentration as well as levels of ADH. Pregnant women and children should be monitored closely during a water deprivation test to ensure that do not lose more than 5 percent of their body weight. A urinalysis may be performed to measure the physical and chemical properties of the urine. In cases of diabetes insipidus, the urine will show a high percentage of water in relation to other substances.
A magnetic resonance imaging (MRI) of the head may be used to identify possible abnormalities situated near the pituitary gland. An MRI is non-invasive and uses radio waves and a magnetic field to create images of the brain tissue. In rare cases, genetic testing may be recommended if the doctor suspects that the diabetes insipidus is caused by an inherited genetic defect.
Treatment & Therapy
Treatment options for diabetes insipidus depend on which form of the condition that the patient has. It may be possible to manage central diabetes insipidus simply by increasing fluid intake. More severe cases are normally treated with a drug called desmopressin. The drug is a synthetic version of the ADH that is lacking in the body. The medication reduces the amount of urination and is typically taken on an “as needed” basis. Too much desmopressin can lead to low blood sodium levels. This can cause nausea, headaches, lethargy, and seizures.
For patients with nephrogenic diabetes insipidus, a low sodium diet can help reduce urine output. They should also drink enough fluids to prevent dehydration. Hydrochlorothiazide, normally used as a diuretic, may also help patients with nephrogenic diabetes insipidus reduce urination.
If the condition is caused by medications, it may be necessary to stop the medication; however, this should only be done on the advice of a doctor. Some cases of gestational diabetes insipidus may be treated with desmopressin. There is no way to treat diabetes insipidus involving an abnormality of the thirst mechanism other than to reduce fluid intake.
Prevention & Prophylaxis
Those living with the condition should take steps to prevent dehydration. This includes having access to water and their medication wherever they go. It is also a good idea for individuals with diabetes insipidus to wear a medical alert bracelet or carry a card in their wallet. In the event of an emergency, this will alert medical providers to the fact that they need special care.