DIABETES INSIPIDUS
Diabetes insipidus is a rare disorder that causes an imbalance of water in the body, resulting in intense thirst and excretion of a large amount of dilute urine.
- Diabetes insipidus doesn’t result in kidney failure or lead to dialysis as the kidney still retains its job of filtering blood. However, it can result in extreme dehydration.
- Diabetes insipidus is not related to diabetes mellitus, meaning that you can have the condition without having diabetes.
CAUSES
To help understand the condition, it may help to first understand how the body uses and regulates fluid.
About 60% of our overall body mass is made up of fluid. For the body to be in overall health, it is important that the body maintains the proper amount of fluid.
While food and water consumption helps to provide fluid to the body, urinating, breathing and sweating helps to eliminate them.
To regulate body fluids, the body uses a system of organs and hormone signals. The kidney plays an important role in this fluid regulation by removing excess body fluids from the bloodstream. This fluid is temporarily stored in the bladder as urine, before urination.
When the fluid regulation system is functioning properly, the kidney conserves fluid and make less urine when the body water decreases, and make too much urine when there is excess body water.
The body makes a substance called antidiuretic hormone (ADH), also called vasopressin, which is produced in the part of the brain called the hypothalamus and stored in the pituitary gland (a small gland located in the base of the brain). The rate of fluid excreted by the kidneys is largely influenced by the production of ADH. When the body starts to become dehydrated, ADH is released into the bloodstream. ADH then leaves the urine concentrated by triggering the kidney tubules to release water back into the bloodstream rather than excreting as much water into the urine.
Any breakdown of this regulation process can result in diabetes insipidus.
There are four different types of diabetes insipidus with different causes. The way in which the system is disrupted determines the type.
Nephrogenic diabetes insipidus occurs when there is damage to the kidney tubules making the kidneys unable to respond properly to ADH. This is caused by:
- Certain genetic defects
- Medications such as lithium
Central diabetes insipidus is the most common form and is caused by damage to the hypothalamus or pituitary gland. This damage affects the production, storage, and release of ADH. This type is due to:
- Head trauma
- Cranial surgery
- Malignant or benign tumor of the brain or pituitary
- In some cases, the cause is unknown.
Dipsogenic diabetes insipidus is caused by intake of excessive fluids usually due to a dysfunction in the thirst mechanism situated in the hypothalamus, resulting in excessive thirst. This type also commonly referred to as the primary polydipsia has also been associated with mental illness.
Gestational diabetes insipidus occurs only in pregnancy. This type is rare and occurs when an enzyme made by the placenta destroys ADH in the mother. The placenta plays an important role in the exchange of nutrients and waste products between a mother and her baby.
SYMPTOMS
- Extreme thirst
- Excessive excretion of undiluted urine.
In infants and young children, symptoms may include:
- Fever
- Weight loss
- Trouble sleeping
- Vomiting
- Diarrhea
- Fussiness and irritability
- Dehydration
DIAGNOSIS AND TREATMENT
To get the most appropriate treatment, the doctor will perform a number of tests to rule out other conditions that share the same symptoms with diabetes insipidus.
Some of the tests the doctor may use to diagnose your condition as well as determine the type you have may include:
- Urinalysis, where a sample of your urine is taken to be tested for salt and other waste concentrations.
- Water deprivation tests. You will be asked to stop taking fluids for a while before the test. Your blood and urine samples are then collected so that the doctor can measure changes in body weight, urine output, urine concentration, ADH blood levels.
- MRI to give a detailed picture of your brain tissues.
- Genetic screening can also be carried out if your doctor suspects an inherited form of the condition.
TREATMENT
Treatment option depends on the type of diabetes insipidus that you have.
A synthetic hormone called desmopressin may be used to treat central and gestational diabetes insipidus.
For nephrogenic type, a low-salt diet may be prescribed to help reduce the amount of urine your kidneys make. To avoid dehydration, you may also need to drink enough water.
There is no specific treatment for the dipsogenic type, other than decreasing fluid intake. If the condition is caused by mental illness, treating the mental illness may help to relieve the symptoms.
If your condition is caused by other problems such as a tumor or a problem with your pituitary, the doctor will have to treat that first.