HealthyCanada.com

Diabetes insipidus (DI) is a rare chronic disorder of the pituitary gland or hypothalamus in which there is an abnormal increase in urine output fluid intake and often thirst. It is sometimes called "water diabetes" to distinguish it from diabetes mellitus or "sugar diabetes". However other than the common symptoms of thirst and increased urination DI is a different condition altogether.

Diabetes insipidus causes frequent urination. The large volume of urine is extremely diluted. To make up for lost water you may feel the need to drink large amounts. You are likely to urinate frequently even at night which can disrupt sleep or on occasion cause bedwetting. Because of the excretion of abnormally large volumes of diluted urine you may quickly become dehydrated if you do not drink enough water. Children with DI may be irritable or listless and may have fever vomiting or diarrhea.

Your body has a complex system for balancing the volume and composition of body fluids. Your kidneys normally remove extra body fluids from your bloodstream. This fluid waste is stored in the bladder as urine. If your fluid regulation system is working properly your kidneys make less urine to conserve fluid when the body is losing water. They also make less urine at night when the body's metabolic processes are slower.

In order to keep the volume and composition of body fluids balanced the rate of fluid intake is governed by thirst and the rate of excretion is governed by the production of antidiuretic hormone (ADH) also called vasopressin. This hormone is made in the hypothalamus a small gland located in the base of the brain. ADH is stored in the nearby pituitary gland and released from it into the bloodstream when necessary. When ADH reaches the kidneys it directs the kidneys to concentrate the urine by returning excess water to the bloodstream and therefore make less urine.

Diabetes Insipidus occurs when this precise system for regulating the kidneys' handling of fluids is disrupted for one reason or another. Consequently there are four types of DI each with a different cause:

Central DI

The most common type of DI is caused by a lack of ADH or vasopressin a hormone that normally acts upon the kidney to reduce urine output by increasing the concentration of the urine. This type of DI is usually due to damage to the pituitary gland where vasopressin is normally produced. Damage to the pituitary gland can be caused by different diseases as well as by head injuries neurosurgery or genetic disorders.

Nephrogenic DI

This type of DI is a result of the kidney's inability to respond to the "antidiuretic effect" of normal amounts of vasopressin. The kidneys' ability to respond can be impaired by lithium and certain other drugs and by chronic disorders such as polycystic kidney disease sickle cell disease kidney failure partial blockage of the small tubes that carry urine from the kidneys to the bladder and inherited genetic disorders. Sometimes the cause of nephrogenic DI is never discovered.

Dipsogenic DI

A third type of DI is caused by a defect in or damage to the thirst mechanism which is located in the hypothalamus. This defect results in an abnormal increase in thirst and fluid intake that suppresses vasopressin secretion and increases urine output.

Gestational DI

Gestational DI occurs only during pregnancy when the pituitary gland is slightly damaged or an enzyme made by the placenta destroys vasopressin in the mother.

Your healthcare providers will want to determine which form of DI is present before starting any treatment.

Some people with DI aren't all that bothered by its symptoms and therefore may need no treatment. There is no evidence that it will lead to other health problems although you will need to ensure that you always drink plenty of fluids to ensure you don't become dehydrated.

If you are inconvenienced by your condition (i.e. sleep is being disrupted by the need to go to the bathroom throughout the night) treatment is available depending on the type of DI you have:

Central DI

To treat the vasopressin deficiency that results from any kind of damage to the hypothalamus or pituitary a synthetic hormone called desmopressin can be taken by an injection a nasal spray or a pill. While taking desmopressin you should drink fluids or water only when you are thirsty and not at other times. This is because the drug prevents water excretion and water can build up now that your kidneys are making less urine and are less responsive to changes in body fluids.

Nephrogenic DI

Desmopressin will not work for this form of DI. Instead you may be given a drug called hydrochlorothiazide (also called HCTZ) or indomethacin. HCTZ is sometimes combined with another drug called amiloride. Again with this combination of drugs you should drink fluids only when you are thirsty and not at other times.

Dipsogenic DI

Desmopressin or other drugs should not be used to treat dipsogenic DI because they may decrease urine output but not thirst and fluid intake. This fluid "overload" can lead to water intoxication a condition that lowers the concentration of sodium in the blood and can seriously damage the brain. Unfortunately because there is no way to correct the underlying abnormality in thirst this type of DI cannot be effectively treated at this time.

Gestational DI

Most cases of gestational DI can be treated with desmopressin. In rare cases however an abnormality in the thirst mechanism causes gestational DI and desmopressin should not be used.