Some patients with Langerhans cell histiocytosis (LCH) develop loss of control of water balance through a deficiency or lack of a hormone, vasopressin, secreted by the pituitary gland.  The disorder is called Diabetes Insipidus (DI).  Areas in the middle of the brain secrete this anti-diuretic hormone that is then stored in the pituitary gland.  In most cases, the portion of the brain that secretes this hormone or the pituitary, which stores the anti-diuretic hormone, has been damaged by the presence of histiocytes.  The hormone is necessary to maintain a proper water balance within the body's cells and blood.

Without normal secretion of the anti-diuretic hormone from the pituitary gland - vasopressin, the kidneys lose excessive water (polyuria) causing increased concentration of the blood and dehydration which leads to thirst.

Not all patients with Langerhans cell hisitocytosis develop Diabetes Insipidus.  Estimates of the percentage of LCH patients that do develop Diabetes Insipidus is around 30% with a range of 5% to 50% reported in different studies.

Occasionally, Diabetes Insipidus occurs before symptoms of LCH, but usually occurs within 4 years from the onset of LCH. 

Diabetes Insipidus and Sugar Diabetes (Diabetes Mellitus) are separate disorders; however, both cause similar symptoms in patients such as, excessive thirst and urination.  DI is caused by lack of the antidiuretic hormone (vasopressin) and sugar diabetes is caused by lack of the hormone insulin. Not only are DI and sugar diabetes separate disorders but the diagnostic tests and treatments are different as well.

Important Note: If the parents note increased urination to NEVER withhold fluid. Sometimes parents see a child waking up to void and then withhold fluid. Although older children will find a way to drink (even if it means drinking from the toilet), younger child may not be able to. Parents should never limit fluid intake until they have seen their physician. Limiting fluid intake without a doctor's recommendation can be very dangerous.