The main symptom of diabetes insipidus is excessive urination, which is also characteristic of persons with type 1 diabetes. However, these two diseases are distinct and unrelated. Diabetes insipidus is caused by a defect in centers in the brain that regulate thirst and urination or by abnormalities in the kidney that make it insensitive to the hormone, vasopressin, also known as antidiuretic hormone. A study in “Pediatrics in Review” reported the incidence of diabetes insipidus in the general population is 3 per 100,000 (See Reference 4).
Classifications
The Diabetes Insipidus Foundation classifies diabetes insipidus into 4 different types that differ in the mechanism by which they are caused (See Reference 1). Neurogenic or central diabetes insipidus is caused by a deficiency in the production and release of vasopressin. Nephrogenic diabetes insipidus is caused by vasopressin resistance in the kidney. Gestational diabetes insipidus only occurs during pregnancy and is caused by increased production of an enzyme in the placenta that breaks down vasopressin. Dipsogenic diabetes insipidus is caused by dysfunctional thirst regulation leading to excessive water intake.
Vasopressin
Vasopressin is synthesized in the hypothalamus in the brain and is stored and released by the posterior pituitary gland. Vasopressin regulates water and salt balance in the body. The main stimulus for its release is an increase in solute concentrations in the blood, also known as blood osmolality. Vasopressin mainly targets the kidneys and increases water reabsorption from the urine.
Signs
The most common sign of diabetes insipidus is colorless urine. Urine testing will detect very low salt concentrations. In children, diabetes insipidus may cause an increase in bed-wetting and infants may cry incessantly and growth may be affected.
Symptoms
The most prevalent symptoms of diabetes insipidus are extreme thirst and excessive urination. An article from the Mayo Clinic reports that normal urine production is approximately 1.5 to 2.5 liters per day and persons with diabetes insipidus excrete between 2.5 and 15 liters per day, depending on the severity of the disease (See Reference 2). The Diabetes Insipidus Foundation stated that besides the risk of dehydration, neurogenic and nephrogenic diabetes insipidus are not associated with any other health risks. Dipsogenic diabetes insipidus has the additional complication of water intoxication. Other symptoms of diabetes insipidus may include constipation and bladder enlargement.
Treatment
The synthetic hormone, desmopressin is used to treat neurogenic and gestational diabetes insipidus and sometimes also dipsogenic diabetes insipidus. In the latter case, authors of a study published in “Clinical and Experimental Nephrology” advocate strict control of water intake (See Reference 3). Desmopressin is ineffective in treating nephrogenic diabetes insipidus because the cells in the kidney are insensitive to it as well as vasopressin. The diuretic, chlorothiazide and the non-steroidal inflammatory drug, indomethacin are commonly used to treat nephrogenic diabetes insipidus, although they have not proven effective in many patients with this disorder.
