What is diabetes insipidus?
Diabetes insipidus is a rare condition in which there is a problem with the secretion of antidiuretic hormone (ADH). ADH, also called vasopressin, controls the amount of water the kidneys release in the urine. ADH is stored in the pituitary gland, which is located behind the bridge of the nose.
Patients with diabetes insipidus have high amounts of urine that is diluted (clear) because of this inability to control the amount of water in the urine. Most cases of diabetes insipidus occur because there isn’t enough ADH, or because the kidneys are not responding properly to ADH.
The body produces more ADH when it is dehydrated or losing blood pressure. The increase in ADH tells the kidneys to hold onto more water instead of releasing it in urine.
For example, if a person without diabetes insipidus were in the desert with no access to water, he or she would produce more ADH hormone and hold water from the urine; a person with diabetes insipidus would continue to urinate the water and would become dehydrated.
It is important to note the difference between diabetes insipidus and other conditions that are associated with an increase in urination, such as diabetes mellitus (high blood sugar) and urinary tract infections.
What health problems are associated with diabetes insipidus?
Most people urinate one to two liters of urine a day, but a person with diabetes insipidus might urinate three liters or more. Patients often wake up in the middle of the night to urinate. Because they are losing a lot of water in the urine, these patients are at risk for dehydration.
Patients who have diabetes insipidus have increased thirst and tend to drink a great deal of water. If the patient has no access to drinking water, he or she cannot make up for the loss of water, and the chemicals in the body get “concentrated.” The person may have increased levels of sodium in the blood (hypernatremia), which cause confusion and other changes in mental status.
What are the types of diabetes insipidus?
There are four types of diabetes insipidus:
- Central diabetes insipidus, the most common form, happens when the brain doesn’t release enough ADH. This can be caused by damage to the pituitary gland or the hypothalamus, a section of the brain near the pituitary gland. The hypothalamus produces ADH and other hormones and controls their release. There are many possible causes of this damage, including an inherited defect in a gene, surgery or injury involving the head, tumors, and infections.
- Nephrogenic diabetes insipidus happens when there is enough ADH, but the kidneys don’t respond to it properly and can’t retain the water. This can be caused by a reaction to a medication, often lithium. It can also be caused by a defect in the genes, a high level of calcium in the blood (hypercalcemia), or kidney disease.
- Dipsogenic diabetes insipidus is not related to ADH, and is caused by drinking too much fluid. It occurs when the mechanism that makes a person feel thirsty is damaged, so the person feels thirsty even when fluid isn’t needed. It can be caused by damage to the hypothalamus or by mental illness.
- Gestational diabetes insipidus affects pregnant women. It is caused by enzymes made by the placenta, a temporary organ that provides nourishment to the fetus. Sometimes these enzymes interfere with the kidneys’ ability to process ADH. Gestational diabetes insipidus usually goes away shortly after the pregnancy is over.
Diagnosis and Tests
How is diabetes insipidus diagnosed?
If your doctor thinks you might have diabetes insipidus, he or she might order one or more of these tests:
- Blood tests
- Urine tests
- Water deprivation test (also called a fluid deprivation test) to see how much urine you produce when you are not drinking anything
- Magnetic resonance imaging (MRI) of your head to examine your pituitary gland
Management and Treatment
How is diabetes insipidus treated?
In some cases, diabetes insipidus cannot be cured, but it can be managed with medications.
Desmopressin, a medication that works like ADH, is often used to treat central diabetes insipidus. Desmopressin can be given as an injection (shot), in a pill, or in a nasal spray. It is also sometimes used to treat gestational diabetes insipidus.
Treatment for nephrogenic diabetes insipidus is more complicated and sometimes involves a combination of approaches. If the condition is caused by medication, sometimes it’s treated by changing the medication. Anti-inflammatory drugs, water pills, and pain medications such as aspirin and ibuprofen can also help. It might take a while to find the right combination for a patient.
Treatments for dipsogenic diabetes insipidus have been less effective. If it is caused by an underlying condition such as mental illness, treatment might be directed at that cause. Some of the same treatments used for other types of diabetes insipidus might also be used.