Diabetes insipidus

Diabetes insipidus (water diabetes) is caused by a reduction in, or failure to respond to, anti-diuretic hormone. This results in passing too much dilute urine and increased thirst.

Alternative names for diabetes insipidus

Water diabetes; DI

What is diabetes insipidus?

Diabetes insipidus occurs when the brain produces little or no <a href='/hormones/anti-diuretic-hormone/'>anti-diuretic hormone</a> (enlarged at upper left), or when anti-diuretic hormone is produced (enlarged at upper right) but the <a href='/glands/kidneys/'>kidneys</a> are insensitive to it (enlarged at centre left).

Diabetes insipidus occurs when the brain produces little or no anti-diuretic hormone (enlarged at upper left), or when anti-diuretic hormone is produced (enlarged at upper right) but the kidneys are insensitive to it (enlarged at centre left).

Anti-diuretic hormone (also called vasopressin) is produced in the hypothalamus and then secreted by the pituitary gland into the bloodstream at the base of the brain. Anti-diuretic hormone is needed to stop the kidneys from producing too much urine.

There are two types of diabetes insipidus, cranial and nephrogenic. Cranial diabetes insipidus is a condition in which the hypothalamus does not produce enough anti-diuretic hormone. Nephrogenic diabetes insipidus is a condition in which the kidneys fail to respond to anti-diuretic hormone. Both conditions mean that the kidneys are unable to retain water, leading to the passing of too much dilute urine (pale urine). This occurs even when the body is dehydrated and should be trying to save fluid by producing concentrated urine (dark urine).

What causes diabetes insipidus?

Usually diabetes insipidus is thought to have no clear, definable cause. This is known as idiopathic. However, some causes can be found:

  1. In cranial diabetes insipidus, the brain produces little or no anti-diuretic hormone. This can be as a result of:
    • head injuries, pituitary tumours or neurosurgery (in these patients, diabetes insipidus may only be short-term)
       
    • conditions that spread through the body (known as infiltrating) such as haemochromatosis and sarcoidosis
       
    • infections such as tuberculosis
       
    • genetic defects (very rare).
       
  2. In nephrogenic diabetes insipidus, the brain is producing enough anti-diuretic hormone but the kidneys are insensitive to it and are unable to produce urine that is dark enough. The causes may be, for example, amyloidosis, polycystic kidneys, medications such as lithium and, very rarely, inherited genetic disorders.
     
  3. Gestational diabetes insipidus – this only occurs in pregnancy and is usually due to enzymes produced from the placenta breaking down anti-diuretic hormone.

What are the signs and symptoms of diabetes insipidus?

The symptoms of diabetes insipidus include:

  1. Too much urine production (polyuria) ranging from 3–18 litres a day. Effectively, this means that the patient will need to go to the toilet a lot.
     
  2. Excessive thirst (polydipsia). This means that the patient will need to drink considerably more than normal.
     
  3. Passing urine too often at night (nocturia). This will affect sleep as the patient will need to get out of bed frequently during the night to pass urine.

These symptoms are similar to those of diabetes mellitus, but there is no sugar present in the urine and blood sugar levels are normal.

Providing there is adequate provision of water to satisfy the excess thirst, the signs of diabetes insipidus can be minimal. Dehydration can occur if fluid intake cannot keep pace with the amount of urine passed.

How common is diabetes insipidus? 

Diabetes insipidus is rare in the general population, affecting approximately one in 25,000 people. In patients who have had pituitary surgery, 10–20% can experience symptoms temporarily after the operation. A similar percentage of patients who have had a severe head injury develop short-term diabetes insipidus. A minority of individuals have persistent symptoms after pituitary surgery and head injury.

Genetic causes of diabetes insipidus are very rare.

Is diabetes insipidus inherited?

In most cases diabetes insipidus is not inherited. Very rarely, it can be due to inherited conditions such as a mutation in the genes that produce anti-diuretic hormone or faults in the genes that produce receptors within the kidney cells that enable anti-diuretic hormone to function.

How is diabetes insipidus diagnosed? 

Certain blood and urine tests can point to a diagnosis of diabetes insipidus such as a high sodium level (hypernatraemia) and high concentration of the blood (serum or plasma osmolality), along with a low urine concentration (urine osmolality).

To be certain of the diagnosis, a ‘water deprivation test’ is commonly undertaken. This takes several hours and involves attending hospital early in the day and being deprived of any fluid intake. Initial blood and urine tests are done to measure the concentration and salt levels in both. At hourly intervals, the same tests are repeated along with measurements such as blood pressure, weight and the amount of urine passed. If the blood sodium or concentration levels rise significantly above normal along with low urine concentration, then it is likely that the patient has diabetes insipidus.

To test if the diabetes insipidus is cranial or nephrogenic, an injection of desmopressin (a manufactured form of anti-diuretic hormone) is given. An hour after this injection is given, the urine concentration is tested again. If there is an increased concentration of more than 50% then cranial diabetes insipidus is most likely. Patients with nephrogenic diabetes insipidus will have a poor response to the desmopressin injection.

If cranial diabetes insipidus is diagnosed, an MRI scan of the head may be performed to look for any obvious abnormality in the hypothalamus (the region of the brain which makes anti-diuretic hormone) or in the pituitary gland (which releases anti-diuretic hormone).

How is diabetes insipidus treated?

All patients diagnosed with diabetes insipidus must ensure they do not become dehydrated and keep drinking plenty of fluids. Cranial diabetes insipidus can be treated with a manufactured version of anti-diuretic hormone, called desmopressin, in the form of a nasal spray or tablet. The dose given and how often medication needs to be taken, will depend on the severity of diabetes insipidus and the symptoms the patient has. In cases of nephrogenic diabetes insipidus, a water tablet (diuretic) called hydrochlorothiazide or amiloride may help, but desmopressin will not.

Are there any side-effects to the treatment?

Side-effects are very rare. Too much desmopressin can lead to low salt levels in the blood and a gathering of excess fluid in the body. This occurs because the desmopressin prevents the kidneys from excreting enough urine. If the patient is concerned about any side-effects, he or she should talk to their endocrinologist or GP.

What are the longer-term implications of diabetes insipidus?

With appropriate treatment, patients with diabetes insipidus should be able to pursue a normal lifestyle. However, it is possible they will require long-term monitoring by their GP and/or endocrinologist. Patients need to be careful to avoid dehydration and keep drinking plenty of fluids.


Last reviewed: Jan 2015