Diabetes insipidus is caused by problems with a chemical called vasopressin (AVP), which is also known as antidiuretic hormone (ADH).
AVP is produced by the hypothalamus and stored in the pituitary gland until needed.
The hypothalamus is an area of the brain that controls mood and appetite.
The pituitary gland is located below your brain, behind the bridge of your nose.
AVP regulates the level of water in your body by controlling the amount of urine your kidneys produce.
When the level of water in your body decreases, your pituitary gland releases AVP to conserve water and stop the production of urine.
In diabetes insipidus, AVP fails to properly regulate your body's level of water, and allows too much urine to be produced and passed from your body.
There are 2 main types of diabetes insipidus:
The 3 most common causes of cranial diabetes insipidus are:
No cause can be found for about a third of all cases of cranial diabetes insipidus.
These cases, known as idiopathic, appear to be related to the immune system attacking the normal healthy cells producing AVP.
It's unclear what causes the immune system to do this.
Less common causes of cranial diabetes insipidus include:
Your kidneys contain nephrons, which are tiny intricate structures that filter waste products from the blood and help produce urine.
They also control how much water is reabsorbed into your body and how much is passed in the urine when you pee.
In a healthy person, AVP acts as a signal to the nephrons to reabsorb water into the body.
In nephrogenic diabetes insipidus, the nephrons in the kidneys are not able to respond to this signal, leading to excessive water loss in large amounts of urine.
Your thirst increases to try to balance this loss from the body.
Nephrogenic diabetes insipidus can be present at birth (congenital) or develop later in life as a result of an external factor (acquired).
These are described in more detail below.
Two abnormal changes in genes that leads to them not working properly (genetic mutations) have been identified that cause congenital nephrogenic diabetes insipidus.
The first, known as the AVPR2 gene mutation, is responsible for 90% of all cases of congenital diabetes insipidus.
But it's still rare, occurring in an estimated 1 in 250,000 births.
The AVPR2 gene mutation can only be passed down by mothers (who may appear to not be affected) to their sons (who are affected).
The remaining 10% of cases of congenital nephrogenic diabetes insipidus are caused by the AQP2 gene mutation, which can affect both males and females.
Lithium is the most common cause of acquired nephrogenic diabetes insipidus.
It's a medication often used to treat bipolar disorder.
Long-term lithium use can damage the cells of the kidneys so they no longer respond to AVP.
Just over half of all people on long-term lithium therapy develop some degree of nephrogenic diabetes insipidus.
Stopping lithium treatment often restores normal kidney function, although in many cases the damage to the kidneys is permanent.
Because of these risks, it's recommended that you have kidney function tests every 3 months if you're taking lithium.
Other causes of acquired nephrogenic diabetes insipidus include: