Diabetes insipidus is a condition that affects the body's ability to regulate its fluid content.

The main symptoms of the condition are:

• Excessive thirst or polydipsia
• Frequent excretion of large volumes of urine or polyuria. In some cases, up to approximately 20 litres of urine may be passed in 24 hours.

Cause

Diabetes insipidus is caused by either inadequate levels or malfunction of antidiuretic hormone (ADH), which is involved in regulating body fluid. Also known of as vasopressin, ADH is manufactured in the hypothalamus and stored in the pituitary gland until its release. In healthy individuals, when the body fluids are depleted, ADH is released from the pituitary gland and prevents the kidneys from excreting fluids in the form of urine.

Among people with diabetes insipidus, however, this process is interrupted in one of two ways, and which way it is interrupted determines which of the following types of diabetes insipidus a patient has:

• Cranial diabetes insipidus - This is the most common type of diabetes insipidus and is caused by an ADH level that is low, usually due to disease, disorder or injury involving the pituitary gland or hypothalamus. Levels of ADH are not high enough to prevent the kidneys from excreting large amounts of urine.
• Nephrogenic diabetes insipidus - This describes when levels of ADH in the body are adequate but the kidneys are not responding to the hormone properly. The condition may be caused by abnormal water channels (aquaporins) in the kidney, by metabolic disorders such as hyperglycemia, or by medications that reduce the expression of aquaporins, such as lithium used to treat bipolar disorder.

Treatment of diabetes insipidus

For mild cranial diabetes insipidus, no treatment may be required and simply drinking enough water may compensate for excessive urination. In more severe cases, a synthetic version of ADH called desmopressin may be prescribed. Another medication that can treat the condition is thiazide diuretics, which reduce the amount of urine produced by the kidneys.