Diabetes Insipidus

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Diabetes insipidus is the condition characterized by polydipsia ( excessive thirst ) and polyuria ( excessive urine volume) due to decreased secretion or resistance to the antidiuretic hormone (ADH) .

What are the types of Diabetes Insipidus ?

Diabetes insipidus is divided into central and nephrogenic diabetes insipidus . Central DI is due to lack of ADH secretion where nephrogenic diabetes insipidus is caused by a failure of the kidneys to respond to antidiuretic hormone.

What causes the Diabetes Insipidus ?

Central DI is caused by Pituitary or hypothalamus gland destruction which includes :

1. Surgery
2. Tumor
3. Meningitis
4. Inflammation
5. Head injury

Nephrogenic DI is caused by:

1. Drugs includes lithium, demeclocycline, amphotericin B
2. Genetic disorder
3. Hypercalcemia ( high levels of calcium in the body)
4. Polycystic kidney disease

Other causes of diabetes insipidus includes :

1. Lung cancer , Leukemia, Lymphoma
2. Histiocytosis X, anorexia nervosa, sarcoidosis
3. Hypoxic encephalopathy
4. Aneurysms
5. Artriovenous malformation

What are the signs and symptoms of Diabetes insipidus ?

1. Polydipsia ( excessive thirst)
2. Polyuria ( excessive urination , 2.5 liters to 15 liter of urination per day )
3. Nocturia ( urinary frequency at night )
4. Fever
5. Vomiting
6. Diarrhea
7. Dry skin
8. Cold extremities
9. Crying, growth retardation , irritability , weight loss in infants
10. Anorexia, Enuresis ( Bed wetting) , growth defects in children

How is a Diabetes insipidus diagnosed ?

Diagnosis relies on clinical findings, laboratory test and radiological imaging .

1. Routine urine test: urine specific gravity 1.005 or less and osmolality of urine is less than 200 mOsm/kg .
2. Water deprivation test
3. Radiological imaging includes MRI may show abnormality of pituitary or hypothalamus gland .

Desmopressin stimulation tests is used to differentiate between the central and nephrogenic diabetes insipidus.

How is a Diabetes insipidus managed ?

Management depends upon the types of the diabetes insipidus.

Treatment of central DI includes:

1. Balanced salt and water intake
2. Avoid dehydration
3. Desmopressin is the drug of choice with the dose of 5-10 U SC per 3-6 hours.

Treatment of nephrogenic DI includes :

1. Low salt diet
2. Stop medication that causes the nephrogenic DI.
3. Hydrochlorothiazide with the dose of 25-50 mg PO per day.
4. Chlorpropamide, carbamazepine and indomethacin are alternatives of Hydrochlorothiazide to treat DI.

What is the prognosis of Diabetes insipidus ?

Prognosis is excellent .

References:

• http://www.emedicinehealth.com
• http://en.wikipedia.org
• http://www.mayoclinic.com
• http://emedicine.medscape.com
• http://www.medicinenet.com
• http://www.ncbi.nlm.nih.gov
• Harrison’s Principles of Internal Medicine, 17^th edition.
• Davidson’s Principles and Practice of Medicine, 20th Edition

Filed Under: Endocrine

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