Diabetes Insipidus: Causes, Symptoms, Diagnosis, Treatment
When is diabetes not really diabetes? When it is Diabetes Insipidus.
Diabetes Insipidus is a rare disorder not related to diabetes mellitus, despite the name and certain similarities of symptoms. The source of diabetes insipidus is not the pancreas, and insulin is not the treatment.
Diabetes insipidus (DI) has several causes. The most common form, called central DI (CDI) is caused by the failure of the hypothalamus to create, or the pituitary gland to store or release, vasopressin, a hormone that regulates the actions of the kidney. Vasopressin is also known as antidiuretic hormone(ADH).
The causes for CDI include: genetic problems; head injury; infection; surgery; or tumor in the pituitary gland or the hypothalamus.
The second most common form of DI is nephrogenic DI (NDI). It occurs when the kidneys or nephrons are insensitive to vasopressin. NDI is a result of a defect in the kidneys, and may be caused by: certain drugs (lithium is one); genetic disorders; high levels of calcium in the body; or kidney disease.
DI can also be triggered by pregnancy, or by excessive alcohol or drug use.
The primary symptoms of DI are unremitting thirst and excretion of excessive amounts of highly dilute urine. Other symptoms might include bed wetting or having to get up multiple times each night to urinate.
Children who have DI might have unusually wet diapers on a consistent basis, and might exhibit fussiness, fever, very dry skin, delayed growth or weight loss.
Diagnosis of DI is by physical examination and urinalysis. There might also be a “water deprivation test”, in which the patient is asked to stop drinking water several hours prior to the administration of the test. The physician will measure changes in weight, urine output and the concentrations of both urine and blood when fluids are withheld. Amounts of ADH in the blood may also be measured.
The physician may also administer ADH during the test.
Treatment of DI varies, depending upon the form of DI the patient has. CDI, caused by a deficiency of ADH, may be treated by prescription of a synthetic hormone called desmopressin. This prescription may be taken orally in the form of tablets, by nasal spray or by injection. If there is an abnormality in the hypothalamus or pituitary gland, like a tumor, that will be treated first.
NDI is a more complicated problem. The physician might prescribe a low-salt diet, which would reduce urine output. Consumption of fluids must be closely monitored to avoid dehydration. There is a drug used as a diuretic, which would normally increase urine output. However, in the case of those with NDI, this same drug often acts to reduce urine output. Anti-inflammatories might also be prescribed.
Both CDI and NDI are treatable, and should have no impact on longevity.