Diabetes Insipidus

Diabetes insipidus is a condition in which there is an imbalance in water in the body. It is a rare condition that leads to intense thirst even after drinking a lot of fluids (polydipsia) and increased urination (polyuria).

It is not related to diabetes mellitus. This condition has no cure, although treatments to relieve thirst and urine output exist.

The most common signs and symptoms of diabetes insipidus include extreme thirst and excretion of large amounts of urine. The amount of urine excreted depends on the severity of the disease. Under normal conditions, a person produces less than 3 quarts (3 liters) of urine per day. However, in diabetes insipidus, the volume of urine produced per day can be as much as 16 quarts (15 liters).

Other signs and symptoms include needing to wake up at night to urinate (nocturia) and bed-wetting. Infants and children with diabetes insipidus may also experience insomnia, fever, vomiting, diarrhea, delayed growth and weight loss.

Another sign of diabetes insipidus in children is unexplained fussiness or inconsolable crying.

Diabetes insipidus is caused when the body can't regulate how it handles fluids.

Normally, the kidneys remove excess body fluids from the bloodstream. This fluid waste is temporarily stored in the bladder as urine, before urinating. When the fluid regulation system is working properly, the kidneys make less urine when the body water is decreased, such as through perspiration, to conserve fluid.

The volume and composition of the body fluids remain balanced through a combination of oral intake and excretion by the kidneys. The rate of fluid intake is largely governed by thirst, although habits can increase the intake far above the amount necessary. 

The rate of fluid excreted by the kidneys is greatly influenced by the production of anti-diuretic hormone (ADH), also called vasopressin. The body makes ADH in the hypothalamus and stores the hormone in the pituitary gland, a small gland located in the base of the brain. ADH is released into the bloodstream when the body starts to become dehydrated. ADH then concentrates the urine by triggering the kidney tubules to release water back into the bloodstream rather than excreting as much water into the urine.

The way in which the system is disrupted determines which form of diabetes insipidus that a patient has:

Central diabetes insipidus

The cause of central diabetes insipidus in adults is usually damage to the pituitary gland or hypothalamus, most commonly due to surgery, a tumor, an illness (such as meningitis), inflammation or a head injury. For children, the cause is often an inherited genetic disorder. In some cases, the cause is unknown.

This damage disrupts the normal production, storage and release of ADH.

Nephrogenic diabetes insipidus

Nephrogenic diabetes insipidus occurs when there's a defect in the kidney tubules — the structures in the kidneys that cause water to be excreted or reabsorbed. This defect makes the kidneys unable to properly respond to ADH. The defect may be due to an inherited (genetic) disorder or a chronic kidney disorder.

Certain drugs, such as lithium and demeclocycline (a tetracycline antibiotic), also can cause nephrogenic diabetes insipidus.

Gestational diabetes insipidus

Gestational diabetes insipidus occurs only during pregnancy and when an enzyme made by the placenta — the system of blood vessels and other tissue that allows the exchange of nutrients and waste products between a mother and her baby — destroys ADH in the mother.

Primary polydipsia

This condition — also known as dipsogenic diabetes insipidus or psychogenic polydipsia — can cause excretion of large volumes of dilute urine. Rather than a problem with ADH production or damage, the underlying cause is intake of excessive fluids. Prolonged excessive water intake by itself can damage the kidneys and suppress ADH, making the body unable to concentrate urine.

Primary polydipsia can be the result of abnormal thirst caused by damage to the thirst-regulating mechanism, situated in the hypothalamus. Primary polydipsia can also be caused by mental illness. In some cases of diabetes insipidus, doctors never determine a cause.

Diagnosis of diabetes can also help doctors to determine the exact type of this disease that the patient has since treatment for each type varies.

Tests used include:

• Water deprivation test - which confirms the diagnosis and help to identify the cause of diabetes insipidus. A patient may be asked to stop drinking fluids for a time so that the body weight, urine output and concentration of urine and blood can be evaluated. Doctors may also measure the level of ADH or administer synthetic ADH during this test. This test should be performed carefully in pregnant women and children to ensure not more than 5 percent of the body weight is lost.
• Urinalysis - in which the physical and chemical properties of urine are analyzed. If urine is les concentrated relative to other excreted substances, it can indicate diabets insipidus.
• Magnetic resonance imagimg (MRI) - a non-invasive test in which powerful magnetic and electrical fields and radio waves are used to make detailed images of the brain to look for abnormalities in or near the pituitary gland.
• Genetic screening may also be performed especially for patients with a family history of diabetes insipidus.

There are various treatments available for diabetes insipidus depending on the type.

• Central diabetes can be treated by administering a synthetic hormone, desmopressin, which acts in the same way that natural ADH works. It can be taken as a nasal spray, as oral tablets or by injection.
  This medication should be taken as needed. It is important to not take more than required since it can lead too much water retention and low low levels of sodium in the blood.
• Nephrogenic diabetes insipidus can be treated by prescribing a low-salt diet for the patient. This reduces the amount of urine that the kidneys produce. Patients should also take enough amounts of water to prevent dehydration from developing.Hydrochlorothiazide, a diuretic, can be used to reduce water secretion in patients with diabetes insipidus. If nephrogenic diabetes insipidus is due to certain drugs, it is necessary to stop taking these medications.
• Gestational diabetes insipidus can be treated with desmopressin. If it is caused by abnormalities with thirst, desmopressin may not be recommended for treatment.
• Primary polydipsia has no specific treatment, other than decreasing the amount of fluid intake. Treating mental illness can relieve the symptoms of primary polydipsia if it is caused by mental illness.

Lifestyle modifications are necessary in order to manage signs and symptoms of diabetes insipidus.

The following tips can help patients with diabetes insipidus to manage signs and symptoms:

• Preventing dehydration by taking enough amounts of fluids.
• Wearing a medical alert bracelet or carrying a medical alert card in the wallet that can help medical personnel to identify that a person has diabetes insipidus.

There are several risks and complications associated with diabetes insipidus.

Nephrogenic diabetes insipidus that is present at birth or develops after birth is inherited from parents. This type of diabetes insipidus affects male, although women can pass the gene to their children.

Complications of diabetes insipidus are connected to dehydration and electrolyte imbalance.

Complications associated with dehydration include:

• Dry mouth
• Changes in skin elasticity
• Low blood pressure (hypotension)
• Elevated blood sodium (hypernatremia)
• Fever
• Headache
• Rapid heartbeat
• Weight loss

Complications associated with electrolyte imbalance include:

• Fatigue and lethargy
• Nausea
• Loss of appetite
• Muscle cramps
• Confusion