Diabetes insipidus

Alternative names:

DI

Definition:

A characterized by pronounced thirst and the passage of large quantities of dilute urine.

Causes, incidence, and risk factors:

Diabetes insipidus is a rare condition that can be caused by a lack of antidiuretic hormone (vasopressin), in which case it is classified as central diabetes insipidus. It can also be caused by a defect in the kidney tubule (nephrogenic diabetes insipidus). Major symptoms are extreme thirst and excessive urine output .

Antidiuretic hormone (vasopressin) is a hormone that is normally produced in the hypothalamus of the brain. It controls the way the kidneys remove, filter, and reabsorb fluids into the blood stream. When there is a lack of this hormone (or when the kidneys cannot respond to the hormone), fluids pass through the kidneys and are lost through urination. Therefore, a person with diabetes insipidus must drink large quantities of water in response to extreme thirst, to compensate for the water loss.

Central diabetes insipidus is caused by damage to the hypothalamus as a result of surgery, infection, tumor, or head injury. Although rare, this is the most common form of DI.

Nephrogenic diabetes insipidus involves a defect in the part of the kidneys (the tubules) that reabsorbs water back into the blood stream. It is much more rare than central DI, and occurs primarily as an inherited disorder that usually affects men, although women can pass the gene on to their children. It can also develop as a complication of other disorders that affect the kidney structures.

If thirst mechanisms are normal and adequate fluids are consumed, there are no significant effects on the fluid and/or electrolyte balance of the body. If inadequate fluids are consumed, the high urine output may cause dehydration and high blood sodium.