Diabetes insipidus

Definition

Diabetes insipidus is caused by the inability of the kidneys to conserve water, which leads to frequent urination and pronounced thirst.

Causes

Diabetes insipidus (DI) is an uncommon condition that occurs when the kidneys are unable to conserve water as they perform their function of filtering blood. The amount of water conserved is controlled by antidiuretic hormone (ADH), also called vasopressin.

ADH is a hormone produced in a region of the brain called the hypothalamus. It is then stored and released from the pituitary gland, a small gland at the base of the brain.

DI caused by a lack of ADH is called central diabetes insipidus. When DI is caused by failure of the kidneys to respond to ADH, the condition is called nephrogenic diabetes insipidus. The major symptoms of diabetes insipidus are excessive urination and extreme thirst. The sensation of thirst stimulates patients to drink large amounts of water to compensate for water lost in the urine.

Central diabetes insipidus is caused by damage to the hypothalamus or pituitary gland as a result of surgery, infection, tumor, or head injury.

Nephrogenic DI involves a defect in the parts of the kidneys that reabsorb water back into the bloodstream. It occurs less often than central DI. Nephrogenic DI may occur as an inherited disorder in which male children receive the abnormal gene that causes the disease on the X chromosome from their mothers.

Nephrogenic DI may also be caused by kidney disease (such as polycystic kidney disease), high levels of calcium in the body (hypercalcemia), and certain drugs (such as lithium, amphotericin B, and demeclocycline).

If thirst mechanisms are normal and adequate fluids are consumed, there are no significant effects on body fluid or salt balance. If inadequate fluids are consumed, the large amount of water lost in the urine may cause dehydration and high sodium levels in the blood.

Symptoms

• Excessive thirst
  • May be intense or uncontrollable
  • May involve a craving for ice water
• Excessive urine volume

Exams and Tests

• Urinalysis
• Urine output:
  • Central DI -- urine output suppressed by a dose of ADH
  • Nephrogenic DI -- urine output not suppressed by a dose of ADH
• MRI of the head

Treatment

The cause of the underlying condition should be treated when possible.

Central diabetes insipidus may be controlled with vasopressin (desmopressin, DDAVP). Vasopressin is administered as either a nasal spray or tablets.

Vasopressin is ineffective for patients with nephrogenic DI. In most cases, if nephrogenic DI is caused by medication (for example, lithium), stopping the medication leads to recovery of normal kidney function.

Hereditary nephrogenic DI is treated with fluid intake to match urine output and drugs that lower urine output. Drugs used to treat nephrogenic DI include the anti-inflammatory medication indomethacin and the diuretics hydrochlorothiazide (HCTZ) and amiloride.

Outlook (Prognosis)

The outcome depends on the underlying disorder. If treated, diabetes insipidus does not cause severe problems or reduce life expectancy.

Possible Complications

Inadequate fluid consumption can result in the following complications:

• Dehydration
  • Dry skin
  • Dry mucous membranes
  • Sunken appearance to eyes
  • Sunken fontanelles (soft spot) in infants
  • Fever
  • Rapid heart rate
  • Unintentional weight loss
• Electrolyte imbalance
  • Fatigue, lethargy
  • Headache
  • Irritability
  • Muscle pains

When to Contact a Medical Professional

Call your health care provider if you develop symptoms that indicate diabetes insipidus.

If you have diabetes insipidus, contact your health care provider if frequent urination or extreme thirst return.