Diabetes insipidus

Diabetes insipidus (DI) is a condition characterized by excessive thirst and excretion of large amounts of severely dilute urine, with reduction of fluid intake having no effect on the concentration of the urine. It is also is a rare disorder that occurs when a person's kidneys pass an abnormally large volume of urine that is insipid—dilute and odourless. Therefore people with diabetes insipidus may feel the need to drink large amounts of liquids.

There are different types of DI, each with a different set of causes. The most common type is diabetes insipidus and diabetes mellitus—which includes both type A and type B diabetes and they are not related, though their conditions are recurrent urination and thirst. Diabetes mellitus causes high blood glucose, or blood sugar, resulting from the body's inability to use blood glucose for energy. People with diabetes insipidus are either having a problem with the production of antidiuretic hormone (central diabetes insipidus) or kidney's response to antidiuretic hormone (nephrogenic diabetes insipidus). DI should not be confused with nocturia.

There are four types of diabetes insipidus. They are

•             Central diabetes insipidus

•             Nephrogenic diabetes insipidus

•             Dipsogenic diabetes insipidus

•             Gestational diabetes insipidus

Central diabetes insipidus

Central diabetes insipidus is mostly as a result from an inherited defect in the gene that produces vasopressin, although this cause is rare. In some cases, the cause is unknown.

Nephrogenic Diabetes Insipidus

Nephrogenic diabetes insipidus is due to the lack of vasopressin production in the hypothalamus due to a range of causes. The underlying causes of Central DI can include vascular, autoimmune, infection, sarcoidosis, some drugs, surgery, head trauma, benign or metastatic pituitary-hypothalamic tumor (particularly originating from breast and lung), although 50% of cases are found to be idiopathic.

Dipsogenic Diabetes Insipidus

A defect in the thirst mechanism, located in a person's hypothalamus, causes dipsogenic diabetes insipidus. This defect results from excessive intake of fluids as opposed to deficiency of arginine vasopressin and increases urine output. The same events and conditions that damage the hypothalamus or pituitary—surgery, infection, inflammation, a tumor, head injury—can also damage the thirst mechanism. Certain medications or mental health problems may predispose a person to dipsogenic diabetes insipidus.

Gestational Diabetes Insipidus

Gestational diabetes insipidus occurs only during pregnancy. In some cases, an enzyme made by the placenta [a temporary organ joining mother and baby] breaks down the mother's vasopressin. In other cases, pregnant women have more prostaglandin, a hormone-like chemical that reduces kidney sensitivity to vasopressin. Pregnant women that develop gestational diabetes insipidus have a mild case that does not cause noticeable symptoms. Gestational diabetes insipidus usually goes away after the mother delivers the baby; however, it may return if the mother becomes pregnant again.

Symptoms of DI

Excessive thirst that may be intense or uncontrollable, usually with the need to drink large amounts of water or craving for ice is typical for DI. The symptoms of excessive urination and extreme thirst are similar to what is seen in untreated diabetes mellitus, with the distinction that the urine does not contain glucose. Blurred vision is a rarity. Signs of dehydration may also appear in some individuals, since the body cannot conserve much (if any) of the water it takes in.

Extreme urination lasts during the day and the night. In children, DI can interfere with appetite, eating, weight gain, and growth, as well. They may exist with fever, vomiting, or diarrhoea. Adults with untreated DI may remain healthy for decades as long as enough water is consumed to offset the urinary losses. However, there is a continuous risk of dehydration and loss of potassium that may lead to hypokalemia.

Ways to diagnose diabetes insipidus

A health care provider can diagnose a person with diabetes insipidus based on the following:

•             Medical and family history

•             Physical exam

•             Urinalysis

•             Blood tests

Medical and Family History

Taking a medical and family history can help a health care provider identify diabetes insipidus. A health care provider asks the patient to evaluates his or her symptoms and ask whether the patient's family has a history of diabetes insipidus or its symptoms.

Physical Exam

Physical exam help’s in identifying diabetes insipidus. Throughout the physical exam, a health care provider regularly inspects the patient's skin and appearance, checking for signs of dehydration.

Urinalysis

This is urine sample. A patient collects the urine sample in a special container at home, in a health care provider's office, or at a commercial facility. A health care provider tests the sample in the same location or sends it to a lab for analysis. The test can show whether the urine is dilute or concentrated. The test can also show the presence of glucose, which can distinguish between diabetes insipidus and diabetes mellitus. The health care provider may also have the patient collect urine in a special container over a 24-hour period to measure the total amount of urine produced by the kidneys.

Blood Tests

A blood test includes getting the patient's blood at a health care provider’s and sending the sample to a lab for analysis. The test measures sodium levels, which can help diagnose diabetes insipidus and in some cases determine the type.

Causes

During the day, your kidneys filter all your blood many times. Normally, most of the water is reabsorbed, and only a small amount of concentrated urine is excreted. Diabetes insipidus occurs when the kidneys cannot concentrate the urine normally, and a large amount of dilute urine is excreted.

ADH is produced in a part of the brain called the hypothalamus. It is then stored and released from the pituitary gland. The amount of water excreted in the urine is controlled by antidiuretic hormone (ADH). ADH is also called vasopressin. This is a small gland just below the base of the brain. Diabetes insipidus caused by a lack of ADH is called central diabetes insipidus. When Diabetes insipidus is caused by the failure of the kidneys to respond to Diabetes insipidus, it is called nephrogenic diabetes insipidus Excessive urine volume: often needing to urinate every hour throughout day and night

Diabetes insipidus is an uncommon condition in which the kidneys are unable to prevent the excretion of water

Treatment and Cure

•             Central diabetes insipidus. A synthetic, or man-made, hormone called decompressing treats central diabetes insipidus. The medication comes as an injection, a nasal spray, or a pill. The medication works by replacing the vasopressin that a patient’s body normally produces. This treatment helps a patient manage symptoms of central diabetes insipidus; however, it does not cure the disease.

•             Nephrogenic diabetes insipidus. In some cases, nephrogenic diabetes insipidus goes away after treatment of the cause. For example, switching medications or taking steps to balance the amount of calcium or potassium in the patient’s body may resolve the problem. Medications for nephrogenic diabetes insipidus include diuretics, either alone or combined with aspirin or ibuprofen. Health care providers commonly prescribe diuretics to help patients’ kidneys remove fluid from the body. Paradoxically, in people with nephrogenic diabetes insipidus, a class of diuretics called thiazides reduces urine production and helps patients’ kidneys concentrate urine. Aspirin or ibuprofen also helps reduce urine volume.

•             Dipsogenic diabetes insipidus. Researchers have not yet found an effective treatment for dipsogenic diabetes insipidus. People can try sucking on ice chips or sour candies to moisten their mouths and increase saliva flow, which may reduce the desire to drink. For a person who wakes multiple times at night to urinate because of dipsogenic diabetes insipidus, taking a small dose of decompressing at bedtime may help. Initially, the health care provider will monitor the patient’s blood sodium levels to prevent hypernatremia, or low sodium levels in the blood.       

•             Gestational diabetes insipidus. A health care provider can prescribe decompression for women with gestational diabetes insipidus. An expecting mother’s placenta does not destroy decompressing as it does vasopressin. Most women will not need treatment after delivery.

Most people with diabetes insipidus can prevent serious problems and live a normal life if they follow the health care provider’s recommendations and keep their symptoms under control.

References

Bichet DG. Polyuria and diabetes insipidus. In: Alpern RJ, Caplan M, Moe OW, eds. Seldin and Giebisch's The Kidney. 5th ed. Philadelphia, PA: Elsevier; 2013:chap 46.

Written by Ruth and Nakelium 

Edited by Nakelium