Diabetes insipidus is a rare condition that causes a person to pass abnormally large amounts of dilute urine. This often makes the person feel very thirsty.
It is caused by problems with a hormone in the body called vasopressin – sometimes known as ADH (anti-diuretic hormone). Vasopressin helps the body to maintain the correct balance of fluids in the blood and urine. When a person has diabetes insipidus, their body can’t properly regulate fluid levels, so too much urine is produced and passed from the body.
Diabetes insipidus isn’t related to the more common forms of diabetes – type 1 and type 2 diabetes mellitus. However, some of the symptoms are similar.
The main symptoms of diabetes insipidus are:
- passing large amounts of dilute urine; and
- feeling extremely thirsty.
The urine may appear very pale, and the person may need to pass urine very often, e.g. several times per hour. The amount of urine that a person passes can vary from about 3 litres to 20 litres per day. This makes the person very thirsty all the time, even though they may drink lots of fluid.
Other symptoms may include:
- feeling weak, tired and irritable
- disrupted sleeping patterns (due to having to get up and pass urine frequently)
- having trouble concentrating.
When children have diabetes insipidus they may also cry inconsolably, grow at a slower rate than expected, lose weight for no apparent reason and have fevers. Many children will also wet the bed at night.
Any adult or child who passes excessive amounts of urine or develops extreme thirst should see a doctor as soon as possible. Other medical conditions can cause these symptoms, and it is important to investigate the possible causes.
Diabetes insipidus occurs when the body can’t regulate fluid levels. This is usually caused either by:
- damage to the pituitary gland or hypothalamus in the brain (known as central diabetes insipidus); or
- a problem in the kidney (called nephrogenic diabetes insipidus).
More rarely, it can be caused by changes during pregnancy (gestational diabetes insipidus) or because a person consumes an excessive amount of fluid. In some cases the cause is unknown.
The anti-diuretic hormone called vasopressin is produced by the hypothalamus and stored in the pituitary gland, located at the base of the brain. When a person starts to become dehydrated, the pituitary gland releases some vasopressin into the blood. The vasopressin signals the kidneys to release stored fluid back into the blood instead of excreting it as urine, thus retaining fluid which helps to maintain hydration.
However, when there isn’t enough vasopressin to tell the kidneys to conserve water, or the kidneys don’t respond properly to the vasopressin, large amounts of dilute urine are passed from the body.
Central diabetes insipidus
When someone has central diabetes insipidus, there is a problem with the production, storage or release of vasopressin. It is often caused by damage to the brain through:
- Complications during brain surgery
- Brain tumour
- Injury to the head
- Autoimmune destruction of the hypothalamus (where the body attacks its own tissue)
- Infections such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membrane surrounding the brain)
- Rare inherited genetic disorders.
Nephrogenic diabetes insipidus
Nephrogenic diabetes insipidus is caused by a problem in the kidneys that makes them unable to respond properly to vasopressin. It means that the kidneys don’t reabsorb fluid as the vasopressin is instructing them to do. It may be caused by:
- Long-term kidney disease
- An inherited genetic disorder
- Use of certain drugs e.g. lithium, some antiviral medications such as foscarnet.
Who gets diabetes insipidus?
Diabetes insipidus is a rare disease, affecting about 1 in 25,000 Australians. It can begin at any age, and affects men and women equally. Central diabetes insipidus is the most common form of the condition.
Tests and diagnosis
Diabetes insipidus symptoms can be similar to other conditions (including type 1 and type 2 diabetes) so a doctor may recommend several tests to diagnose the problem.
This may involve:
- A urine test: To check the concentration of water, electrotypes and other substances.
- A water deprivation test: A person is asked not to drink any fluid for several hours to see how their body responds. Someone with diabetes insipidus will keep passing large amounts of dilute urine, while someone without the condition will usually pass less urine, which will be more concentrated.
- Vasopressin test: This can help to identify what type of diabetes insipidus a person has, and may be done at the same time as the water deprivation test. A doctor gives the person an injection of vasopressin to see how the body responds. If it causes the person to stop producing urine, then the problem is probably due to a shortage of vasopressin (central diabetes insipidus). If the person keeps producing urine after receiving vasopressin, the problem is more likely to be in the kidneys (nephrogenic diabetes insipidus).
- MRI scan of the head: This may be done to check for damage or defects in the pituitary gland or surrounding areas.
- Genetic screening: In some cases, a doctor may recommend genetic testing if there is a family history of excessive urination.
A formal water deprivation test is not generally needed where there is an obvious cause such as head injury or pituitary surgery.
The main complications of diabetes insipidus are:
- Dehydration: a serious lack of fluid in the body
- Electrolyte imbalance: the concentration of minerals called electrolytes (e.g. calcium, potassium, magnesium) may go up when the body can’t retain enough fluid.
People may also develop confusion, dizziness and sluggishness if they have severe dehydration. If these symptoms are present, the person should seek immediate medical attention.
In very mild cases no treatment for diabetes insipidus may be necessary as long as the person has easy access to water and can drink enough to stay hydrated. However, many cases will require treatment to reduce the amount of urine produced by the body.
Treatment for central diabetes insipidus often involves taking a synthetic form of the hormone vasopressin to restore urine output to normal. Desmopressin (Minirin, Octostim) or vasopressin (Pitressin) are the medicines used in Australia. They may be taken as a tablet, wafer, injection or nasal spray or nasal solution.
In mild cases of nephrogenic diabetes insipidus, dietary changes may be helpful (e.g. reducing the amount of salt and protein the diet). Medicines known as diuretics can be used to reduce the volume of urine passed. In cases of nephrogenic diabetes insipidus caused by medications, the doctor may suggest stopping or changing these – but no one should stop medication unless they have been advised to by their doctor.
What should I do if I have diabetes insipidus?
People with diabetes insipidus can work in partnership with their doctors to manage the condition and treat the underlying cause appropriately. It is important to prevent dehydration and to take medication as prescribed by your doctor. It may also be helpful to carry some form of medical alert card or wear a MedicAlert bracelet so that others are aware of your condition.