Diabetes insipidus

Diabetes insipidus is a rare condition where you produce a large amount of urine and often feel thirsty.

Diabetes insipidus isn't related to diabetes mellitus (usually just known as diabetes), but it does share some of the same signs and symptoms.

The two main symptoms of diabetes insipidus are:

• thirst (polydipsia)
• passing large amounts of urine even at night (polyuria)

In very severe cases of diabetes insipidus, up to 20 litres of urine can be passed in a day.

Read more about the symptoms of diabetes insipidus.

When to seek medical advice

You should always go to see your GP if you're feeling thirsty all the time. Although it may not be diabetes insipidus, it should be investigated.

Also see your GP if you're passing more urine than normal. Most healthy adults pass urine four to seven times in a 24 hour period.

Children tend to urinate more frequently because they have smaller bladders. However, seek medical advice if your child urinates more than 10 times a day.

Your GP will be able to carry out a number of tests to help determine what's causing the problem.

Read more about diagnosing diabetes insipidus.

What causes diabetes insipidus?

Diabetes insipidus is caused by problems with a hormone called antidiuretic hormone (ADH), also known as vasopressin.

ADH plays a key role in regulating the amount of fluid in the body. It's produced by specialist nerve cells in a part of the brain known as the hypothalamus. ADH passes from the hypothalamus to the pituitary gland where it's stored until needed.

The pituitary gland releases ADH when the amount of water in the body becomes too low. It helps retain water in the body by reducing the amount of water lost through the kidneys, making the kidney produce urine that's more concentrated.

In diabetes insipidus, the lack of production of ADH or, in rare cases, the kidney not responding to ADH, means the kidney can't make enough concentrated urine and too much water is passed from the body.

People feel thirsty as the body tries to compensate for the increased loss of water by increasing the amount of water taken in.

Read more about the causes of diabetes insipidus.

Types of diabetes insipidus

There are two main types of diabetes insipidus which are described below.

Cranial diabetes insipidus

Cranial diabetes insipidus occurs when there's not enough ADH in the body to regulate urine production.

Cranial diabetes insipidus is the most common type of diabetes insipidus. It can be caused by damage to the hypothalamus or pituitary gland – for example, after an infection, operation, brain tumour or head injury.

In about one in three cases of cranial diabetes insipidus there's no obvious reason why the hypothalamus stops making enough ADH.

Nephrogenic diabetes insipidus

Nephrogenic diabetes insipidus occurs when there's enough ADH in the body but the kidneys fail to respond to it. It can be caused by kidney damage or, in some cases, inherited as a problem on its own.

Some medications, particularly lithium (used to treat serious mental health conditions, such as bipolar disorder), can cause nephrogenic diabetes insipidus.

Treating diabetes insipidus

Treatment isn't always needed for mild cases of cranial diabetes insipidus. You just need to increase the amount of water you drink to compensate for the fluid lost through urination.

If necessary, a medication called desmopressin can be used to replicate the functions of ADH.

Nephrogenic diabetes insipidus is often treated with medications called thiazide diuretics which reduce the amount of urine the kidneys produce.

Read more about the treating diabetes insipidus.

Complications

As diabetes insipidus causes excessive urination, the amount of water in the body can become low. This is known as dehydration.

Rehydration solutions can be used to treat mild dehydration. Severe dehydration will need to be treated in hospital.

Read more about the complications of diabetes insipidus.