A note about thirst and water balance in your body
Getting the balance right between how much water your body takes in and how much water your body passes out is very important. This is because a large proportion (about 70%) of your body is actually water. Also, water levels in your body help to control the levels of some important salts, particularly sodium and potassium.
Your body normally controls (or regulates) water balance in two main ways:
- By making you feel thirsty and so encouraging you to drink and take more water in.
- Through the action of a hormone called antidiuretic hormone (ADH) which controls the amount of water passed out in your urine.
ADH is also known as vasopressin. It is made in a part of your brain called the hypothalamus. It is then transported to another part of your brain, the pituitary gland, from where it is released into your bloodstream. After its release, ADH has an effect on your kidneys. It causes your kidneys to pass out less water in your urine (your urine becomes more concentrated).
So, if your body is dehydrated (lacking in water), your thirst sensation will be triggered, encouraging you to drink. As well as this, more ADH will be released by your pituitary gland, so reducing the amount of water that is passed out in your urine. However, if you have too much water on board already, your thirst sensation will be switched off, removing your desire to drink and take in more water. At the same time, less ADH will be released by your pituitary gland, so increasing the amount of water that is passed out in your urine (your urine becomes more diluted).
What is diabetes insipidus and what causes it?
Diabetes insipidus is a condition in which your ability to control the balance of water within your body is not working properly. Your kidneys are not able to regulate how much water passes out in your urine as well as normal. This means that you pass large amounts of dilute urine. The medical term for passing large amounts of urine is polyuria.
Because you are passing more urine, and therefore losing more fluid from your body, to try to compensate for this, you become more thirsty and want to drink more. The medical term for this increased thirst and desire to drink more is polydipsia.
If you have diabetes insipidus you can become dehydrated easily. The levels of sodium and potassium salts in your blood can also become imbalanced and too high.
There are two different types of diabetes insipidus (described below):
- Cranial diabetes insipidus.
- Nephrogenic diabetes insipidus.
Note: diabetes insipidus should not be confused with the much more common type of diabetes, diabetes mellitus. The two conditions are not related. Diabetes mellitus can also make you feel thirsty and pass lots of urine. It occurs when the level of glucose (sugar) in your blood becomes higher than normal. In diabetes insipidus, there is no problem with the level of glucose in your blood. Separate leaflets, ‘Diabetes Type 1’ and ‘Diabetes Type 2’ give further details about diabetes mellitus.
Cranial diabetes insipidus
Cranial diabetes insipidus occurs when your brain produces or releases a reduced amount of ADH. As mentioned above, ADH usually helps your kidneys to concentrate your urine. If less ADH is released, you will pass an increased volume of dilute urine.
Cranial diabetes insipidus can occur if your hypothalamus or pituitary gland is damaged, causing ADH production and release to be reduced. Some of the causes of cranial diabetes insipidus include:
- Head injury.
- Malignant (cancerous) or benign (noncancerous) tumours of your brain or pituitary gland.
- Surgery to your brain around the region of the pituitary gland and hypothalamus.
- Idiopathic diabetes insipidus. In this condition the cells in your hypothalamus become damaged and stop producing ADH. In many cases, the damage is thought to be due to an autoimmune problem. Normally, your body makes antibodies to fight infections – for example, when you catch a cold or have a sore throat. These antibodies help to kill the bacteria, viruses or germs causing the infection. In autoimmune diseases your body makes similar antibodies (autoantibodies) that attack its normal cells. In this case, the cells of your hypothalamus are attacked by autoantibodies.
- Infections including encephalitis and meningitis.
- Some rare inherited conditions.
Cranial diabetes insipidus may just be a problem on its own. However, sometimes it can occur with other problems because the production of other hormones that are released by the pituitary gland is also affected. Cranial diabetes insipidus is sometimes called central diabetes insipidus or neurogenic diabetes insipidus.
If cranial diabetes insipidus is caused by a head injury or surgery to your brain, it may only be a problem for a short period of time, perhaps a few weeks, and then the condition can improve.
Nephrogenic diabetes insipidus
The term nephrogenic refers to the kidneys. In nephrogenic diabetes insipidus, ADH is still being released by your brain but your kidneys, for some reason, become resistent to the effects of ADH. This means that ADH is not able to work properly to allow your kidneys to concentrate your urine. Again, this means that you will develop polyuria (where you pass large amounts of diluted urine) and polydipsia (where you are excessively thirsty and so drink more).
Nephrogenic diabetes insipidus is very rare. Causes include the following:
- Some chronic kidney diseases and chronic (persistent) kidney failure.
- If the level of certain drugs that you are taking becomes too high in your body, particularly a drug called lithium.
- Rarely, nephrogenic diabetes insipidus can be passed on through your genes.
How common is diabetes insipidus and who gets it?
Diabetes insipidus is not a very common condition. It affects about 1 in 25,000 people.
Diabetes insipidus can affect people of any age but it is mostly a problem that affects adults.
What are the symptoms of diabetes insipidus?
The main symptoms of diabetes insipidus include:
- Passing large volumes of urine. You may find that you can pass somewhere between 3 and 20 litres of urine per day.
- Passing urine frequently (up to every half an hour) during the day.
- Getting up to pass urine frequently during the night.
- Feeling excessively thirsty, despite the fact that you seem to be drinking lots of fluids.
- Dehydration (a lack of water in your body). This can become a problem if you do not drink enough fluids to compensate for the amount of urine that you are passing. Symptoms of dehydration can include headaches, dry mouth, lips and tongue, dry skin, dizziness or light-headedness, muscle cramps, weakness, confusion and, in severe cases, collapse. (Severe dehydration is a medical emergency and immediate medical attention is needed.)
- Tiredness and reduced concentration. This may be due to lack of sleep because of repeated night-time trips to the toilet.
Poor growth and weight loss may be noticed in babies with diabetes insipidus. They may also appear irritable and difficult to settle. Older children may have problems with bedwetting at night-time and also incontinence of urine during the daytime. They may also have poor growth and a loss of appetite as well as tiredness.
How is diabetes insipidus diagnosed?
Your doctor may suspect diabetes insipidus by your typical symptoms and because of other things – for example, if you have had a recent head injury, surgery to your brain, etc. In order to confirm the diagnosis, various tests are usually suggested. These can include the following.
Blood and urine tests
- To check the levels of sodium and potassium salts in your blood. These can be high in diabetes insipidus.
- To check the level of glucose in your blood and urine to exclude diabetes mellitus.
A water deprivation test
This is a special test where you must not drink any water or other fluids for a certain period of time (usually around 6-8 hours). The volume of urine that you produce will be measured to see if there is any change in the amount. If your body is working normally, the amount of urine that you produce should reduce if you have not drunk anything for a long time. However, if you have diabetes insipidus, there will be little change in your urine production.
Antidiuretic hormone test
After the period of fluid deprivation, you may then be given a drug that is similar to ADH. If you have cranial diabetes insipidus, once you have been given this drug, the amount of urine that you produce should reduce. The drug is replacing the ADH that you are lacking. If you have nephrogenic diabetes insipidus, you may have no, or only a small, response to the drug.
Other tests may sometimes be suggested to look for possible causes of diabetes insipidus. For example, an MRI scan of your brain and pituitary gland.
What is the treatment for diabetes insipidus?
Cranial diabetes insipidus
The underlying cause of cranial diabetes insipidus may need treating first. For example, if you are found to have a tumour affecting your hypothalamus or pituitary gland. Your doctor will be able to advise any treatment that you may need.
Otherwise, the following may be suggested:
- Careful control of the fluids that you drink. In mild cases, cranial diabetes insipidus may be controlled by ensuring that you are drinking enough fluid to quench your thirst and to keep the salt levels in your blood stable. You may not need any other treatment. Regular monitoring of the salt levels in your blood using blood tests will usually be suggested.
- Desmopressin. This is a drug that resembles ADH. It can have the same effect as ADH on your kidneys. Desmopressin is also known as DDAVP®. It is usually given as nasal drops or nasal spray, or it can be taken as tablets by mouth. You usually need to take desmopressin between one and three times a day. The correct dose for you will be decided by your doctor. The aim is that the drug should replace the ADH that your body is lacking and so will help to control the amount of urine that you pass.
Sometimes cranial diabetes insipidus may only last for a short period (perhaps a few weeks) after a head injury or brain surgery and so treatment may only be needed in the short term. However, other causes may mean that you need lifelong treatment for diabetes insipidus.
Nephrogenic diabetes insipidus
As mentioned above, sometimes nephrogenic diabetes insipidus can be caused as a side-effect of certain drugs such as lithium. If you are taking such a drug and you develop diabetes insipidus, your doctor may recommend that the drug be changed. However, only make changes to your medication on the advice of your doctor.
Nephrogenic diabetes insipidus is not caused by a lack of ADH and so giving desmopressin will not treat the condition. If you have mild nephrogenic diabetes insipidus, your doctor may suggest that you drink plenty of fluids to avoid dehydration and they may also suggest some changes to your diet to help reduce the amount of urine that you produce. For example, eating fewer salty and processed foods and fewer foods that contain protein (such as meat, fish and eggs). You may be referred to a dietician for specialist advice about your diet. You should not make changes to your diet without the advice of an expert.
If you have more severe nephrogenic diabetes insipidus, medication may be suggested. For example, a drug called hydrochlorothiazide. This drug can help to reduce the amount of urine that your kidneys produce.
Some other considerations and advice
If you have diabetes insipidus and you develop diarrhoea and/or vomiting, you need to pay particular attention to make sure that you drink plenty of fluids to help prevent dehydration. If you have any vomiting and/or serious diarrhoea, you should see a doctor. You also need to take care in hot weather because you will sweat more and so may become dehydrated more easily.
But it is also important that you don’t become overloaded with water. This can happen if you are drinking more fluids than you are passing out in your urine or if you are taking too much desmopressin. Water overload can lead to problems with the levels of salts in your blood, particularly sodium. It can make your sodium levels drop too low. Signs that you may be water overloaded can include headaches, weight gain and dizziness. Low sodium levels can make you feel drowsy and confused and in severe cases can lead to a fit (seizure) and unconsciousness. You should see your doctor if you are concerned about any of these symptoms. To avoid this, never take more desmopressin than you need and, if you are taking desmopressin, follow the advice of your doctor about how much fluid you should drink. Also, your doctor will usually recommend regular blood tests to check on your sodium and other salt levels if you have diabetes insipidus.
It is a good idea to wear a MedicAlert® or equivalent bracelet if you have diabetes insipidus. This is so that healthcare professionals know about your condition, even if you have an accident or are unwell and become unconscious and so are not able to tell them yourself.
Further help and information
The Pituitary Foundation
PO Box 1944, Bristol BS99 2UB
Support and Information Helpline: 0845 450 0375 (Monday-Friday 9.00 am-5.00 pm)
The Pituitary Foundation is a national UK charity which is working to provide information and support to those living with pituitary disorders, including patients, their relatives, friends and carers. They also provide information and advice about diabetes insipidus.
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