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Diabetes insipidus - Pituitary · PDF fileDiabetes insipidus 3 What is diabetes insipidus (DI) and why do we get it? Diabetes insipidus (DI) is caused by a problem with either the

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The Pituitary Foundation Information Booklets

Working to support pituitary patients, their carers & families



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Diabetes insipidus

2 Diabetes insipidus

The Pituitary Foundation is a charity working in the United Kingdom and Republic of Ireland supporting patients with pituitary conditions, their carers, family and friends.

Our aims are to offer support through the pituitary journey, provide information to the community, and act as the patient voice to raise awareness and improve services.

About this bookletThe aim of this booklet is to provide information about diabetes insipidus.

You may find that not all of the information applies to you in particular, but we hope it helps you to understand your condition better and offers you a basis for discussion with your GP and endocrinologist.

What is diabetes insipidus and why do we get it? 3

The two forms of diabetes insipidus 5

How is DI diagnosed and treated? 7

How is DI diagnosed? 7

What tests are carried out and how will they feel? 7

How is DI treated? 7

Aftercare 9

How will diabetes insipidus affect my life? 10

Prescriptions 10

Driving 10

Employment problems 10

Insurance & pensions 10

Personal medical identification 11

Toilet facilities card 11

National key scheme 11

Common questions 12-13

What DI means to me - a patient's story 14

Membership & donation information 15

Diabetes insipidus 3

What is diabetes insipidus (DI) and why do we get it?

Diabetes insipidus (DI) is caused by a problem with either the production, or action, of the hormone vasopressin (AVP). If you have DI your kidneys are unable to retain water. This leads to the production of large volumes of urine and, in turn, greatly increased thirst. DI can occur at any age, but is mostly found in adults. It is a rare disorder, affecting only about 1 in 25,000 people.

To understand DI we need to understand a little about how the body regulates water balance - the difference between how much water the body takes in and how much it passes out. Water balance is very important for the body. A large proportion of what we are is made up of water. In addition, the amount of water we have in our circulation is a large factor in determining the balance of salt in our bodies. As with any function that is important, the body has a sensitive mechanism for regulating water balance. Like any good mechanism it is also simple, involving two key components:

Vasopressin (AVP or ADH - anti-diuretic hormone) - which regulates the amount of water passed out of the body in urine.

Thirst and drinking - which determines the amount of water the body takes in.

AVP (sometimes called Anti-diuretic hormone or ADH) is a hormone released from the rear most part of the pituitary gland (the posterior pituitary). This gland is located at the base of the brain, and is about 3 to 5 centimetres behind the bridge of the nose. AVP circulates in the bloodstream and acts on the kidneys to reduce the amount of water that is passed out in urine.

How AVP and thirst work together is best described with the help of the bath tub analogy. As with a bath tub, the body likes to keep the level of water it contains at the right level for its purposes. There are only two ways the level of water can be altered: Watercanbeletintothebaththroughturning

the taps on; just as thirst and drinking can allow more water into the body

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Watercanbeletoutofthebaththroughtakingthe plug out; just as the body can let more water out by reducing the amount of AVP produced and so letting more water to be passed out of the body as urine

Unlike a bath tub, the body is very good at sensing the level of water it has on board. If it does not have enough and is dehydrated, it triggers us to drink more through activating the thirst (turning on the taps). At the same time, it makes more AVP and so reduces water loss in

urine (it puts the plug in). On the other hand, if the body senses the level of water is too much, it turns the thirst off (turning taps off) and makes less AVP (taking the plug out of the plug hole). The level of water is therefore maintained through a combined approach.

Together, AVP and thirst maintain water balance very effectively in both situations where water is either easy to find, or is scarce. DI occurs when this mechanism regulating water balance breaks down.

What is diabetes insipidus (DI) and why do we get it?

Diabetes insipidus 5

What is diabetes insipidus (DI) and why do we get it? The two forms of diabetes insipidus (DI)

1. Cranial diabetes insipidus (CDI)CDI is caused by the partial or absolute lack of AVP. The lack of AVP means that the kidneys cannot retain the amount of water that the body needs them to, and produces a lot of dilute urine. The body is therefore reliant on only one of its two mechanisms to keep the amount of water in the body at the correct level, thirst and drinking. People with CDI are thirsty all of the time; they pass large amounts of urine frequently through the day and often have to pass urine several times at night.

Sometimes CDI occurs on its own and however in many cases, it is accompanied by loss of other hormones made by the pituitary. This may be through a problem in the development of the pituitary gland; a tumour within or near the gland; or the result of an accident, or surgery to, or near to, the gland.

CDI following pituitary surgery may be temporary, only lasting a week or two. In some cases it may be permanent.

2. Nephrogenic diabetes insipidus (NDI)NDI is a condition in which the kidneys do not respond to the normal signal (AVP) to reduce water loss. Thus, the kidneys are not able to absorb the water that passes through them.

The primary symptoms of NDI are polyuria (passage of large volumes of urine) and polydipsia (excessive thirst and drinking).

Inherited NDI may show up in the first weeks of life. Symptoms can include irritability, failure to thrive, lack of appetite and vomiting. Investigation can reveal high blood levels of sodium. Up to 90% of the cases of inherited

NDI are the result of mutations affecting the AVP-receptor (V2R) that is needed for the kidney to respond to AVP and reabsorb water. The remaining cases are the result of mutations in the pore in kidney cells through which water is reabsorbed (AQP2). Though each type of inherited NDI has a different genetic cause, the symptoms of each are the same.

Males are the most likely to display symptoms of X-linked NDI, whereas males and females are equally likely to display symptoms of the autosomal recessive form of NDI. This is because the V2R gene is carried on the X-chromosome and males have only one X-chromosome. A problem with a gene on this single X-chromosome cant be counter-balanced by another normal X-chromosome (the position in females). Autosomal recessive NDI is carried on a non-sex chromosome, so males and females are equally likely to inherit the problem.

Acquired NDI is the more common form of NDI and can occur at any time of life. Most often, acquired NDI is a result of the use of the drug lithium. Acquired NDI can also result from the use of other drugs, such as colchicine, methoxyflurane, amphotericin B, gentamicin, loop diuretics and demeclocycline. It can also occur as a result of certain diseases and physical conditions, which can result in either permanent or temporary NDI such as: chronickidneyfailure otherkidneydiseases abnormallylowlevelsofpotassium abnormallyhighlevelsofcalcium sicklecelldisease

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Treatment of NDIThere is as yet no cure for inherited NDI. Currently, NDI is managed by: ensuringreadyaccesstowater followingalow-sodium(andsometimeslow-

protein) diet, and using thiazide diuretics, alone or in

combination with a prostaglandin inhibitor or a potassium-sparing diuretic, to reduce the volume of urine output.ThiazidediureticscanreduceanNDIpatient's

polyuria, but theymay alsodeplete thebody'sstores of potassium. This depletion can cause other symptoms and may be dangerous. When takingthiazidediuretics,thepatient'spotassiumlevels must be monitored. To maintain sufficient potassium in the body, the addition of potassium supplements or amiloride (but not both) to the treatment regime may be required.

DI is not related to diabetes mellitusIt is very important to point out that DI is not related to the type of diabetes most people have heard of - DIAbetes MellItUs which is very common and can also cause symptoms of passing a lot of urine and being thirsty. In DI, there is NO problem with the level of sugar in the blood or urine. This is very important as friends, relatives and health care workers may make assumptions about the condition you have, based on the more common condition.

What does it feel like to have DI?The main symptoms that you will feel are thirst (no matter how much you drink) and the need to pass urine very frequently, even during the night. You will pass large volumes of urine; you may pass as much as 4 - 10 litres of urine a day. It is important that you do not try to prevent this by ignoring your thirst and drinking less, or you will disturb the balance of water in your body.

You may well have symptoms of dehydration, for example feeling shivery and nauseous with headaches. People with DI have mentioned that their excessive thirst can be compared with eating 4 or 5 dry cream crackers one after the other, without any drinks.