Diabetes Insipidus

Signs & symptoms

The primary symptoms of diabetes insipidus are excessive thirst and excessive urination, sometimes as often as every 15 minutes. This is caused by the lack of antidiuretic hormone (ADH), also called vasopressin, or the inability of the kidneys to respond to ADH.

Because of the excessive consumption of fluids, your urine may be very clear, like water. Most people with this condition become so thirsty that they drink enough water to replace all of the fluid they urinate and avoid dehydration.

Diagnosis

To diagnose diabetes insipidus, your doctor will ask you questions about your health and that of other family members, particularly if your doctor suspects you have the inherited form of the disease. Tests that may be administered include:

• Urinalysis. This test examines the contents of your urine. If the water content is high and the salt and waste concentration low, it could be due to diabetes insipidus.
• Fluid or water deprivation test. This is a test to measure changes in your body weight, urine output and urine contents. Prior to this test, your doctor will measure your weight and collect a urine sample for analysis. Your doctor will ask you to stop drinking fluids for several hours. During this period, urine samples will be collected. Your doctor also may measure the blood levels of antidiuretic hormone (ADH) or vasopressin. For children and pregnant women, it's important that no more than 5 percent of body weight is lost during the test.
• Magnetic resonance imaging (MRI). An MRI scan of the head may be performed to look for abnormalities in or near the pituitary gland. This scan uses powerful magnets and radio waves to create detailed images of the brain.

Treatments

The medication used to treat this disorder is called desmopressin acetate (DDAVP), which is similar to the antidiuretic hormone (ADH), also called vasopressin, produced by your body. DDAVP comes in several forms. Your doctor will work with you to prescribe the one that works best for you. The different forms are:

• Nasal spray. This is medication is squirted into your nostril. A dose is usually taken at bedtime so you can sleep through the night uninterrupted. Some people may require a dose during the day.
• Rhinal tube solution. This form of the medication is stored in the refrigerator at all times. A small tube is used to deliver very precise doses of medication into your nose. Though the medication can be more difficult to deliver through the rhinal tube, you can vary the dose of the medication as needed. It can be more helpful for those who have a varying schedule or who need very small doses. Both this form and the nasal spray are delivered into your nostril for very rapid absorption into the bloodstream. Clean your nostrils with a tissue before administering the medication for better absorption.
• Pills. Pills are convenient but they take longer to take effect. You won't feel your thirst dissipate as quickly as you would by taking the spray or rhinal tube. For some patients, pills aren't as effective in controlling symptoms. It's important to follow directions in taking this medication. Most people take a dose at bedtime so they sleep through the night comfortably. You may find that you sometimes need a dose during the day to control your symptoms or that your needs change when you're ill, particularly if you have a stuffy nose, when the DDAVP spray may not be absorbed as well. You don't have to take the DDAVP every day at the same time.

Don't take the medication if you don't need it. Take your medication when you are:

• Urinating excessively or your urine is as clear as water
• Excessive thirsty

If you take too much DDAVP or take it when you don't need it, your body may retain too much fluid and you may develop a condition called hyponatremia, which can be life-threatening. Warning signs of this disorder include decreased thirst and urination, headache, nausea, fatigue and confusion.

If you feel that your symptoms aren't being controlled or if you experience some of the warning signs of hyponatremia, contact your doctor so your medication dose can be adjusted. If properly treated, you should be able to maintain your normal lifestyle and activities.