What is diabetes insipidus?
Diabetes insipidus (DI) is an endocrine disorder involving deficient production or lack of effective action of an antidiuretic hormone (ADH or vasopressin). ADH is made in the hypothalamus (lower part of the brain), stored in and secreted by the pituitary gland (a small gland located below the hypothalamus), and works on the kidney to conserve fluid. Deficient production of ADH or lack of effective action of ADH causes large amount of urine output, increasing thirst, dehydration, and low blood pressure in advanced cases. Average urine volume for a normal adult is 1.5 liters daily. In diabetes insipidus, the urine volume can approach 18 liters daily!
Diseases of the hypothalamus/pituitary gland causing lack of ADH production is called central DI. Diseases of the kidney causing lack of response of the kidney to fluid conserving action of ADH is called nephrogenic DI.
Examples of central DI include surgical removal of the hypothalamus, tumors of the hypothalamus or the pituitary gland, infection of the pituitary gland, autoimmune (body’s immune system attacking own organ) damage of the pituitary gland, and familial disease of the pituitary gland.
Examples of nephrogenic DI include certain kidney diseases. Low blood potassium level, protein starvation, high blood calcium level, sickle cell anemia, medications (such as lithium, demeclocycline,and methoxyflurane).
How is diabetes insipidus diagnosed?
Diagnosis of DI involve excluding other causes of large urine volume such as diabetes mellitus (a condition with high blood glucose because of lack of insulin). The tests to confirm DI are too complicated to be discussed here. They are usually carried out and interpreted by internists or endocrinologists. After confirming presence of DI, tests are then performed to search for the underlying cause. In the future, blood ADH level can be measured and will likely simplify the diagnosis of DI.
How is diabetes insipidus treated?
Treatment of central DI involves administering the missing ADH hormone. A synthetic ADH called DDAVP can be administered by injection or inhaled nasally. Recently, DDAVP has become available in pill form. Properly treated, patients with central DI can restore urine volume towards normal levels and do well. Long term prognosis of many patients with central DI are good, some actually spontaneously improve over time. To achieve optimal outcome, it is important for patients to work closely with their doctors to accurately diagnose the condition, identify the underlying cause, and start treatment.
Diabetes Insipidus: A deficiency of circulating antidiuretic hormone (ADH), or (vasopressin), or because the kidneys are not responding properly to the presence of ADH. It affects both sexes, and more common in childhood or early adulthood. In uncomplicated diabetes insipidus, the prognosis is good. With adequate water replacement, patients usually lead normal lives. In cases complicated by an underlying disorder, such as metastatic cancer, the prognosis varies.
Diabetes insipidus is marked by frequent urination, as frequently as every half hour, all day and night. Resulting in the need to keep drinking – huge quantities.
Cause: Diabetes insipidus may be familial, acquired, or idiopathic. It can be acquired as the result of intracranial neoplastic or metastatic lesions. other causes may include hypophysectomy or other neurosurgery; head trauma, which damages the neurohypophyseal structures; infection; granulomatous disease; and vascular lesions.
Extreme polyuria (frequent urination) usually 4 to 16 liters/day of dilute urine, but sometimes as much as 30 liters/day with low specific gravity (less than 1.005)
Extreme thirst and increase fluid intake
Fatigue (in severe cases)
Dehydration – may have increase heart rate, low blood pressure, dry mouth, eyes may appear sunken, lack of tears, weight loss, confusion and irritability
Until the underlying cause of diabetes insipidus can be identified and eliminated, administration of various forms of vasopressin or of a vasopressin stimulant can control fluid balance and prevent dehydration.
Chlorpropamide may be prescribed to stimulate ADH secretion.
Call your doctor if you have the above symptoms and or signs of dehydration as soon as possible.
Diabetes mellitus: A chronic insulin deficiency or resistance, diabetes mellitus is marked by disturbances in carbohydrate, protein, and fat metabolism. Diabetes is a major risk factor for myocardial infarction, cerebrovascular accident, renal failure, and peripheral vascular disease. It is also the leading cause of new blindness in adults.
Diabetes mellitus occurs in two forms: insulin-dependent diabetes mellitus (IDDM) also called: Type I, or juvenile-onset diabetes and the more prevalent non insulin-dependent diabetes mellitus (NIDDM), also called Type II, or maturity-onset diabetes.
Type I diabetes: Usually occurs before age 30 (although it may occur at any age). The patient is usually thin and will require exogenous insulin and dietary management to achieve control.
Type II diabetes: usually occurs in obese adults after age 40 and is most frequently treated with diet and exercise, may also requires hypoglycemic drugs. Treatment may also include insulin therapy.
In diabetic ketoacidosis (DKA) or hyperglycemic hyperosmolar nonketotic coma (HHNC), dehydration may cause hypovolemia and shock. Long-term effects of diabetes may include retinopathy, nephroopathy, artherosclerosis, and peripheral and autonomic neuropathy. Peripheral neuropathy usually affects the legs and may cause numbness.
Cause: Both Types I and II are of unknown cause but may be hereditary.
Type I appears to be an autoimmune disease and is strongly associated with human leukocyte antigens (HLA) DR 3 and 4. It may also be associated with certain viral infections.
Type II is associated with impaired insulin secretion, peripheral insulin resistance, and increased basal hepatic glucose production. Other associated factors include obesity; insulin antagonists such as excess counter regulatory hormones and phenytoin; oral contraceptives; and pregnancy.
Polyuria (frequent urination) related to hyperglycemia
Polydipsia (excessive thirst)
Dry mucous membranes
Poor skin turgor
Type II, weight loss and polyphagia (excessive ingestion of food)
Effective treatment attempts to normalize blood glucose levels and prevent complications.
Type I – Insulin replacement that mimics normal pancreatic function. Current means of insulin replacement include mixed, split doses of rapid (short-onset) with intermediate – or long-onset insulin injected usually twice a day (varies according to doctors orders); premeal injections of rapid insulin with intermediate -onset injections at bedtime; and continuous subcutaneous insulin infusion (insulin pump) (NOTE – this is a example, all medications should be prescribed and follow your doctors orders)
Pancreas transplantation, is still experimental.
Diabetic therapy also requires a diet carefully planned to meet nutritional needs, to control blood glucose levels, and to reach and maintain appropriate body weight.
For the obese diabetic patient, weight reduction is a dietary goal. In Type I, the calorie allotment may be high, depending on growth stage and activity level. To be successful, however, the diet must be followed consistently, and meals must be eaten at regular times.
Type II diabetes may require oral hypoglycemics. These medications stimulate endogenous insulin production and may also increase insulin sensitivity at the cellular level.
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