Diabetes insipidus

Central diabetes insipidus also called pituitary diabetes insipidus is a deficiency of a hormone called arginine vasopressin or antidiuretic hormone which leads to disproportionate urine production. ^{[1] [2]} Although it bears the name of diabetes, central diabetes inspidius is entirely different from diabetes mellitus although both may manifest with frequent urination. ^[2]

Epidemiology

1 out of 25,000 people are affected. There is no gender predilection. ^[2]

Causes

A specialized structure located in the brain called hypothalamus produces the hormone vasopressin. The hormone is stored in another nearby structure called pituitary gland and functions in urine concentration. Central diabetes insipidus may be brought about by injuries to the mentioned brain structures. These injuries may be due to surgery, infection or tumor.

When there is lack of vasopressin, the kidneys which rely on it cannot perform its function aptly leading to rapid loss of water from the body in the form of urine. The urine being created is dilute and the person experiences severe thirst.

In cases when the individual gets the disease at early age, genetic component is suspected to be an underlying cause. ^[2]

Signs and Symptoms

An affected person has excessive urine production especially at night with the urine appearing pale and colorless. The person can have bedwetting and he or she drinks markedly great quantities of water. When there is dehydration, the person may have confusion and alteration in sensorium or level of consciousness. Children can have fever, weight loss and growth failure. Vomiting and irritability can be present as well. ^{[2] [3]}

Diagnosis

Urinalysis is done routinely to check for sugar as central diabetes insipidus may mimic diabetes mellitus. Urine examination will show a low salt concentration. The most definitive exam is a water deprivation test. An MRI may also be performed to study structures like pituitary gland. ^[2]

Treatment

The condition is often lifelong however the symptoms are manageable thru medications that sustain fluid balance. Vasopressin or desmopressin is given which is available as nasal spray, oral tablet or injectable drug. Other drugs can be given like chlorpropamide and carbamazepine. ^[1]

References:

1.      http://www.merckmanuals.com/home/hormonal_and_metabolic_disorders/pituitary_gland_disorders/central_diabetes_insipidus.html

2.      http://diabetes.webmd.com/guide/central-neurogenic-diabetes-insipidus-symptoms-causes-and-treatments

3.      http://www.nlm.nih.gov/medlineplus/ency/article/000460.htm