Diabetes insipidus: Excessive urination and extreme thirst as a result of inadequate output of the pituitary hormone ADH (antidiuretic hormone, also called vasopressin) or the lack of the normal response by the kidney to ADH.
There are two types of diabetes insipidus -- central and nephrogenic. Central diabetes insipidus is a lack of ADH production and is due to damage to the pituitary gland or hypothalamus where ADH is produced. Nephrogenic diabetes insipidus is lack of response of the kidney to the fluid-conserving action of ADH. Nephrogenic diabetes insipidus can be due to diseases of the kidney (such as polycystic kidney disease), certain drugs (such as lithium), and can also occur an inherited disorder.
In both central and nephrogenic diabetes insipidus, patients excrete extraordinarily large volumes of very dilute urine. They feel thirsty and drink very large amounts of water to compensate for the water they lose in the urine. The main danger with diabetes insipidus comes when fluid intake does not keep pace with urine output, resulting in dehydration and high blood sodium.
The treatment of central diabetes insipidus is with vasopressin used as a nasal spray or as tablets. Nephrogenic diabetes insipidus does not respond to vasopressin treatment. In cases of nephrogenic diabetes insipidus caused by a drug (such as lithium), stopping the drug usually leads to recovery. In cases of hereditary nephrogenic diabetes insipidus, treatment is with fluid intake to match urine output and drugs that lower urine output. Effective treatment is important because the dehydration and high blood sodium can cause brain damage and death.