Diabetes Insipidus

Symptoms

The 2 main symptoms of diabetes insipidus are often needing to pee a large amount of urine and feeling extremely thirsty.

If you have diabetes insipidus, you may pee pale, watery urine every 15 to 20 minutes. 

The amount of urine can range from 3 litres in mild cases to up to 20 litres per day in severe cases.

It's also likely that you'll feel thirsty all the time and have a "dry" feeling that's always present, no matter how much water you drink.

If you need to pee regularly and always feel thirsty, your sleeping patterns and daily activities may be disrupted. This can cause tiredness, irritability and difficulty concentrating, which can affect your daily life further. You may also feel generally unwell and "run down" much of the time for no apparent reason.

Symptoms in children

Excessive thirst can be difficult to recognise in children who are too young to speak.

Signs and symptoms that could suggest diabetes insipidus include:

• excessive crying
• irritability
• slower than expected growth
• high body temperature (hyperthermia)
• unexplained weight loss

In older children, symptoms of diabetes insipidus include:

• wetting the bed (enuresis) – although most children who wet the bed do not have diabetes insipidus
• loss of appetite
• feeling tired all the time (fatigue)

Causes

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

AVP 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. AVP passes from the hypothalamus to the pituitary gland, where it's stored until needed. 

The pituitary gland releases AVP 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 kidneys produce more concentrated urine.

In most cases of diabetes insipidus, the lack of production of AVP means the kidneys cannot make enough concentrated urine and too much water is passed from the body. This is called AVP deficiency (previously called cranial diabetes insipidus).

In rare cases, the kidneys do not respond to AVP. This causes a specific form of diabetes insipidus called AVP resistance (formerly nephrogenic diabetes insipidus).

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

Diagnosis

See your GP if you have the symptoms of diabetes insipidus. They'll ask about your symptoms and carry out a number of tests. You may be referred to an endocrinologist (a specialist in hormone conditions) for these tests.

As the symptoms of diabetes insipidus are similar to those of other conditions, including type 1 diabetes and type 2 diabetes, tests will be needed to confirm which condition you have.

If diabetes insipidus is diagnosed, the tests will also be able to identify the type you have, arginine vasopressin deficiency (AVP-D) or arginine vasopressin resistance (AVP-R).

Water deprivation test

A water deprivation test involves not drinking any liquid for several hours to see how your body responds.

If you have diabetes insipidus, you'll continue to pee large amounts of dilute urine when normally you'd only pee a small amount of concentrated urine. During the test, the amount of urine you produce will be measured.

You may also need a blood test to assess the levels of antidiuretic hormone (ADH) in your blood.

Your blood and urine may also be tested for substances such as glucose (blood sugar), calcium and potassium.

If you have diabetes insipidus, your urine will be very dilute, with low levels of other substances.

A large amount of sugar in your urine may be a sign of type 1 or type 2 diabetes rather than diabetes insipidus.

Vasopressin test

After the water deprivation test, you may be given a small dose of vasopressin (AVP), usually as an injection.

This will show how your body reacts to the hormone, which helps to identify the type of diabetes insipidus you have.

If the dose of AVP stops you peeing urine, it's likely your condition is the result of a shortage of AVP.

If this is the case, you may be diagnosed with AVP-D.

If you continue to pee despite the dose of AVP, this suggests there's already enough AVP in your body, but your kidneys are not responding to it.

In this case, you may be diagnosed with AVP-R.

MRI scan

An MRI (Magnetic Resonance Imaging) scan is a type of scan that uses a strong magnetic field and radio waves to produce images of the inside of the body, including your brain. 

You may need an MRI scan if your endocrinologist thinks you have cranial diabetes insipidus as a result of damage to your hypothalamus or pituitary gland.

If your condition is caused by an abnormality in your hypothalamus or pituitary gland, it may need to be treated too, along with treatment for diabetes insipidus.

Treatment Options

Treatment is not always needed for mild cases of AVP-D. 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 AVP.

AVP-R is often treated with medications called thiazide diuretics, which reduce the amount of urine the kidneys produce.

When To See A Doctor

You should always 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:

• peeing more than normal – most healthy adults pass urine 4 to 7 times in a 24-hour period
• needing to pee small amounts at frequent intervals – sometimes this can occur along with the feeling that you need to pee immediately

Children tend to pee more frequently because they have smaller bladders. But seek medical advice if your child pees 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.