Diabetes Insipidus

Introduction

Diabetes insipidus (DI) is a disorder characterized by intense thirst and by the excretion of large amounts of urine (polyuria). In most cases, it's the result of your body not properly producing, storing or releasing a hormone that increases water absorption by your kidneys and decreases urine flow. This form of diabetes insipidus is often called central diabetes insipidus, or sometimes neurogenic diabetes insipidus.

Diabetes insipidus can also occur when your kidneys are unable to properly respond to the hormone — a condition referred to as nephrogenic insipidus. Still rarer forms can occur during pregnancy (gestational diabetes insipidus).

Treatment depends on which type of diabetes insipidus you have.

Signs and symptoms

The two most common signs of diabetes insipidus are:

• Extreme thirst
• Excretion of an excessive volume of diluted urine

• Unexplained fussiness or inconsolable crying
• Unusually wet diapers
• Fever, vomiting or diarrhea
• Dry skin with cool extremities

• Central DI. The cause of central diabetes insipidus is damage to the pituitary gland or hypothalamus due to surgery, a tumor, illness (such as meningitis), inflammation or a head injury. In some cases the cause is unknown. This damage disrupts the normal production, storage and release of ADH.
Nephrogenic DI. Nephrogenic diabetes insipidus occurs when there's a defect in the kidneys tubules — the structures in your kidneys that cause water to be excreted or reabsorbed. This defect makes your 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 tetracycline, also can cause nephrogenic DI. In about one in four cases of nephrogenic DI, doctors never determine a cause.
Gestational DI. 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.

• Central DI. Because the cause of this form of diabetes insipidus is a lack of antidiuretic hormone (ADH), treatment is usually with a synthetic hormone called desmopressin. You can take desmopressin as a nasal spray, oral tablets, or by injection. The synthetic hormone will eliminate the increase in urination. For most people with central DI, desmopressin is a safe and effective treatment. If the condition is caused by an abnormality in the pituitary gland or hypothalamus (such as a tumor), however, your doctor will first treat the abnormality.
  If you have central diabetes insipidus, be sure to replace any fluid that you do lose; however, while you're taking desmopressin, drink fluids or water only when you're thirsty. This is because the drug prevents excess water excretion, which means your kidneys are making less urine and are less responsive to changes in body fluids.
  In mild cases of central diabetes insipidus, increased water intake may be all that you need. Your doctor may suggest a certain amount of water intake (usually more than 2.5 liters a day) to ensure proper hydration.
• Nephrogenic DI. This condition is the result of your kidneys not properly responding to ADH, so desmopressin is not a treatment option. Instead your doctor may prescribe a low-salt diet to help reduce the amount of urine your kidneys make. You'll also need to be sure to drink enough water to avoid dehydration.
  The drug hydrochlorothiazide, used alone or with other medications, may improve symptoms. Although hydrochlorothiazide is a diuretic (usually used to increase urine output), in some cases it can reduce urine output for people with nephrogenic DI.
  If symptoms from nephrogenic diabetes insipidus are due to medications you're taking, stopping these medicines may help; however, don't stop taking any medication without talking with your doctor first.
• Gestational DI. Treatment for most cases of gestational diabetes insipidus is with the synthetic hormone desmopressin. In rare cases, an abnormality in the thirst mechanism causes gestational diabetes insipidus. In these rare cases, doctors don't prescribe desmopressin.