Central diabetes insipidus is a condition in which you do not have enough antidiuretic hormone. Having abnormally low amounts of this hormone makes your kidneys produce too much urine. There is a risk that you could become dehydrated unless you drink large amounts of water.
Antidiuretic hormone is often called ADH for short. It is made in an area of your brain known as the hypothalamus, and stored in another part of your brain called the posterior pituitary gland. When your body needs to save fluids—perhaps when you are in a hot place and have been losing a lot of water through sweating—the pituitary gland releases ADH. The hormone travels in your bloodstream to your kidneys. It causes them to reduce the volume of urine they produce so that your body saves more water.
If you have central diabetes insipidus, you have a problem with ADH production, storage, or release. This means that your body is less able to reduce its urine output, even when you need to save water.
Another type of diabetes insipidus can occur if you have a kidney problem that prevents your kidneys from responding to ADH. This condition is known as nephrogenic diabetes insipidus.
Anything that damages the parts of your brain involved in making or storing ADH can cause central diabetes insipidus. This could include:
- brain surgery
- head injuries
- brain tumors
- blocked or swollen arteries in the brain
- certain rare genetic conditions
Some people have what is described as an idiopathic form of the disease. This means that it occurs without any obvious cause. In this form of the disease, it is thought that your body’s immune system mistakenly destroys the cells in your hypothalamus. It is not known why this happens.
Although it can occur at any age, the condition most often affects adults.
Symptoms of the disease can start suddenly or develop slowly. They may include:
- feeling very thirsty
- frequent urination
- passing large volumes of urine
- having to urinate at night
- symptoms of dehydration, such as confusion, headaches, and dizziness
You may need to have blood tests to check that you do not have diabetes mellitus (“sugar” diabetes). In diabetes mellitus, you cannot control your blood sugar levels. Blood tests can also measure the levels of your blood salts, such as sodium and potassium, which can be raised in central diabetes insipidus.
Urine tests may be done to check for diabetes mellitus, and also to measure how concentrated or dilute your urine is.
You will probably have to take a water deprivation test. During the test, which lasts for several hours, you will not be allowed to drink any water. Your urine will be tested, and your weight checked, at regular intervals. Normally, when people limit their water intake, their urine output falls. However, if you have central diabetes insipidus, you may continue to produce large volumes of urine.
At the end of the test, the doctor may inject you with synthetic ADH. If you have central diabetes insipidus, your urine output should then fall. In people with the nephrogenic disease, their kidneys do not respond to the ADH and no change in urine output is seen. The test helps your doctor to decide which type of diabetes insipidus you have.
MRI (magnetic resonance imaging) scans of your brain may be carried out to look for problems such as tumors. Your doctor might also order genetic tests if he or she suspects that an inherited disease is causing your diabetes insipidus.
The treatment you receive will vary according to the cause of your condition, its severity, and your general health.
If your condition is mild, you may be able to control it by monitoring how much fluid you drink. If you choose to do this, you may need regular tests to check the levels of salts in your blood.
If the condition is more severe, you may need to go on medication to help control your ADH levels.
Some people will need to take a synthetic version of ADH every day in order to replace the natural hormone, which is missing. This may be taken in the form of tablets, a nasal spray, or skin injection.
If your condition is not severe, you may be able to take medication, which boosts your body’s own production of ADH.
With treatment, your outlook is likely to be positive. You may be advised to wear a special bracelet which can alert medical professionals to your condition in an emergency.