Diabetes insipidus
What is diabetes insipidus?
Diabetes insipidus, sometimes called water diabetes, is a rare endocrine (hormonal) condition. The symptoms of diabetes insipidus are an excessive thirst, passing large amounts of dilute urine and a general feeling of weakness.
Although similar in name to diabetes mellitus (sugar diabetes), diabetes insipidus is a completely unrelated condition.
What causes diabetes insipidus?
Diabetes insipidus can be caused either by a defect in the hypothalamus or the pituitary gland in the brain (central diabetes insipidus) or a defect in the kidney (nephrogenic diabetes insipidus).
These defects cause problems with a hormone called anti-diuretic hormone (ADH, also known as vasopressin). ADH is secreted by the hypothalamus and pituitary gland and affects the functioning of the kidney, where it is responsible for reabsorption of water. For various reasons, this doesn’t happen in diabetes insipidus and the body doesn’t retain water but instead passes large volumes of very dilute urine. Someone with diabetes insipidus may pass up to 18 litres of urine a day compared with a healthy person's 1.5 litres.
Central diabetes insipidus
Central diabetes insipidus is caused by not having enough ADH (anti-diuretic hormone).
When there isn’t enough ADH to tell the kidneys to conserve water, large amounts of dilute urine are passed; the person has a pronounced thirst, will become dehydrated, and in advanced cases will develop low blood pressure.
What causes central diabetes insipidus?
Central diabetes insipidus is generally caused by damage to the hypothalamus and/or pituitary gland, both of which are located in the brain. This damage may be a result of:
- brain surgery;
- autoimmune destruction of the hypothalamus;
- brain tumour;
- injury to the head;
- infections such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membrane surrounding the brain); or
- rare causes such as genetic disorders causing inherited disease.
People with this condition drink large amounts of fluid because of the extreme thirst that occurs in response to the water loss.
Nephrogenic diabetes insipidus
Nephrogenic diabetes insipidus is not caused by a lack of ADH but by the kidneys failing to respond to the message that ADH is telling them — which is to reabsorb water.
What causes nephrogenic diabetes insipidus?
Nephrogenic diabetes insipidus can be a result of chronic (long-lasting) kidney disease. It can also be due to a rare inherited disorder called congenital nephrogenic diabetes insipidus. Theis disorder more commonly affects men, but women can carry the gene and pass it to their children. Rarely, pregnant women can develop diabetes insipidus during their pregnancy — this is known as gestational diabetes insipidus.
Other causes include:
- low blood-potassium levels;
- high blood-calcium levels;
- sickle cell anaemia; and
- medicines such as lithium (used to treat bipolar mood disorders) and tetracycline (an antibiotic).
As with central diabetes insipidus, excessive amounts of watery (dilute) urine are passed and excessive thirst causes a high intake of fluids. If, however, inadequate fluids are consumed the excessive amounts of dilute urine passed may cause dehydration.
In approximately 30 per cent of cases of diabetes insipidus, no cause is found.
How is diabetes insipidus treated?
In very mild cases no treatment for diabetes insipidus may be necessary. However, in most cases of central diabetes insipidus a synthetic form of the missing ADH hormone (desmopressin) is given by tablet, injection or by nasal spray. If treated appropriately, people with central diabetes insipidus can restore their urine output to normal and some even find that their condition improves spontaneously over time.
In cases of nephrogenic diabetes insipidus, medications are used to reduce the volume of urine passed, while the levels of salts (such as sodium) in the blood must be monitored closely. Dietary changes may be advised.
What you should do if you have diabetes insipidus
It is important for people with diabetes insipidus to work with their doctors to accurately diagnose the severity of the condition and the underlying cause, and to decide on the form of treatment.
People with diabetes insipidus should wear some kind of medical identification, such as a MedicAlert bracelet.
Last Reviewed: 14 September 2009
- 1. eMIMS Prescribing Information, October 2009
2. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Diabetes insipidus [updated 2008, Sep; accessed 2009, Sep 18). Available from: http://kidney.niddk.nih.gov/kudiseases/pubs/insipidus/index.htm
3. Therapeutic Guidelines (eTG). Hypopituitarism. In: Endocrinology guidelines [updated 2009, Jun; accessed 2009, Sep 17]. Available from: http://www.tg.org.au
4. MayoClinic.com. Diabetes insipidus [updated 2008, Sep 6; accessed 2009, Sep 17]. Available at: http://www.mayoclinic.com/health/diabetes-insipidus/DS00799
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