Diabetes Insipidus (DI) is a rare disorder that can occur as a consequence of histiocytosis involving the pituitary gland. It should not be confused with the more common diabetes mellitus, also known as sugar diabetes, which results from too much sugar in the blood. Although both disorders have similar symptoms, in every other way including the cause and treatment, they are completely unrelated diseases. The rate of occurrence for DI is not known, because there has been no organized method to count the number of patients.
Diabetes Insipidus is a result of damage to the pituitary gland, a small gland at the base of the brain which stores and releases a hormone called ADH (antidiuretic hormone), also known as vasopressin. This hormone normally causes the kidney to control the amount of water released as urine from the body. When the pituitary is damaged, the kidneys lose too much water (increased urination), which then leads to increased thirst.
The connection between Histiocytosis and Diabetes Insipidus was first reported in the late 1800s. Since then, DI has been recognized as a characteristic feature of LCH. It is known to also occur in other histiocytic disorders, such as Rosai Dorfman and JXG.
It is believed that approximately between 5% and 50% of LCH patients develop DI depending on the extent of disease. The risk of developing DI in patients with multisystem LCH is 4 to 6 times more than those with single-system disease. Patients with skull, facial, and/or eye bone lesions are at much higher risk of developing DI. This risk is increased further if LCH remains active for a longer period or if it recurs.
Diabetes Insipidus is recognized by a great increase in the amount of urine passed (often several gallons per day) and an increased thirst. Any patient with known LCH with an increase in drinking habits or passing large amounts of urine should be tested for DI.
Diabetes Insipidus is diagnosed with a water deprivation test, which measures changes in body weight, blood values, urine output, and urine composition when fluids are withheld over a several-hour period. It is very important that this test be supervised by a knowledgeable physician in a medical setting. An x-ray test called an MRI scan is sometimes performed to see if there is change in the brain and pituitary area, but this test alone cannot diagnose DI.
Diabetes Insipidus is usually a permanent, lifelong condition and cannot be cured. However, the symptoms of constant thirst and urination can be well controlled with treatment with DDAVP, a synthetic kind of vasopressin, and normal, symptom-free quality of life can be restored.