Diabetes Insipidus (DI)

Diabetes insipidus (DI) is a rare disorder that causes a person to frequently urinate, which commonly results from inadequate secretion of antidiuretic hormone (ADH). Because of the large volume of fluid lost in the urine, the person with the condition tends to drink large amounts of fluid. This would likely make the person urinate frequently, even at night that it can disrupt sleep and, occasionally, cause bedwetting.

The condition can lead to dehydration if fluid lost is not replaced. In children, diabetes insipidus may cause a child to be irritable or listless and may have fever, vomiting, or diarrhea.

Milder forms of DI can be controlled by drinking enough water. The condition rarely causes severe complications.

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Diabetes Insipidus (DI) and Diabetes Mellitus (DM): The difference.

Although some of their signs and symptoms are similar, such as excessive thirst and excessive urination, DI and DM are unrelated.

Diabetes mellitus is more common and results from insulin deficiency or resistance, which leads to high blood glucose. DI does not cause blood sugar to become elevated.

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Fluid Regulation in the Body

The kidneys remove harmful materials and extra body fluids from the blood. These fluids are stored in the bladder as urine. When the fluid regulation system is working properly, the kidneys make less urine to conserve fluid when water intake is decreased or water is lost. Also, the kidneys make less urine at night because, during this time, the body’s metabolic processes are slower.

The rate of fluid intake is governed by thirst and the rate of excretion is governed by the production of antidiuretic hormone. These processes make sure that the volume and composition of body fluids are balanced. The hormone antidiuretic hormone, also called vasopressin, is made by the hypothalamus, which is a small endocrine organ in the brain. ADH is stored in the pituitary gland and is released into the blood when it is needed. ADH directs the kidneys to concentrate the urine by reabsorbing some of the filtered water to the bloodstream. As a result, less urine is formed. Diabetes insipidus occurs when this precise system for regulating the kidney’s handling of fluid becomes disrupted.

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Types

There are several types of diabetes insipidus including:

Central DI

This is the most common type of serious DI. Central DI occurs when the pituitary gland is damaged causing disruption in the normal storage and secretion of ADH. Head injuries, neurosurgery, some genetic disorders, and other health problems can cause damage to the pituitary gland.

Nephrogenic DI

This type of DI occurs when the kidneys are not able to respond to ADH. Some drugs such as lithium can affect the ability of the kidneys to respond to ADH. Chronic diseases, such as polycystic kidney disease, kidney failure, sickle cell disease may also cause Nephrogenic DI, and some inherited genetic diseases. In some cases of nephrogenic DI, the cause is unknown.

Dipsogenic DI

Dipsogenic DI occurs when the thirst center located in the hypothalamus is damaged or defective. As a result, the abnormal increase in thirst and fluid intake suppresses ADH secretion. Consequently, the decline ADH secretion causes an increase in urine output.

Gestational DI

This type happens only during pregnancy. It occurs when the ADH in the mother is destroyed by an enzyme made by the placenta. The placenta is composed of blood vessels and other tissues, which develops with the fetus. It allows exchange of nutrients and waste products between the mother and fetus.

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Diagnosis

Sometimes, the doctor may suspect that a patient with diabetes insipidus has diabetes mellitus. This is partly because DM is more common and DM and DI have similar symptoms. However, thorough testing should make the diagnosis clear. In addition, the doctor must determine which type of DI a patient has before proper treatment can begin.

Diagnosis of DI is based on a series of tests, which may include urinalysis and a fluid deprivation test. In some patients, imaging tests such as magnetic resonance imaging (MRI) of the brain may also be necessary.

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Treatment

Treatment of diabetes insipidus depends on the type of DI a patient has.

Central DI

This type is treated with a synthetic hormone called desmopressin, which is similar to the effects of ADH. The synthetic hormone can be taken through an injection, nasal spray, or a pill. The drug prevents water excretion. While taking the drug, a person should drink fluids only when thirsty.

Nephrogenic DI

Nephrogenic DI is treated with hydrochlorothiazide (HCTZ), indomethacine, or a combination of HCTZ and amiloride.

Dipsogenic DI

Experts have not yet discovered an effective treatment for dipsogenic DI.

Gestational DI

Most cases of gestational DI can be treated with desmopressin. However, desmopressin should not be used when gestational DI is due to an abnormality in the thirst center.

Reference:
National Kidney and Urologic Diseases Information Clearinghouse (September 2008). Diebetes Insipidus (NIH Publication No. 08—4620). National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda, MD. Web URL: http://kidney.niddk.nih.gov/kudiseases/pubs/insipidus/index.htm. Accessed: November 17, 2008

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