Persistent, unrelenting thirst can indicate a rare but serious endocrine disorder — diabetes insipidus. Anatomist Dan Baumgardt, Senior Lecturer at the University of Bristol’s School of Psychological Science and Neuroscience, explained this in The Conversation.

“Diabetes insipidus is very different from the more well-known diabetes mellitus. It has nothing to do with blood glucose levels. Instead, it is caused by problems with the antidiuretic hormone (ADH),” the researcher said.

This hormone, also known as arginine vasopressin (AVP), regulates the body’s water balance. It helps the kidneys retain water, especially during dehydration. When this system malfunctions — for example, due to ADH deficiency — the body loses too much fluid even if the person drinks large amounts of water. This leads to constant thirst, dehydration, and frequent urination.

Baumgardt noted that there are several forms of diabetes insipidus. The central type is linked to insufficient production of the hormone in the hypothalamus. Another form is dipsogenic diabetes insipidus, in which the brain’s thirst center is impaired.

“If this center is damaged — by trauma, tumor, or infection — a person may experience relentless thirst. This leads to excessive water intake, which in turn suppresses ADH production and creates a vicious cycle,” he added.

The danger is that too much water intake can lower sodium levels in the blood to dangerous levels. This can cause headaches, confusion, seizures, and in severe cases — death.

Sometimes the symptoms of diabetes insipidus are mistaken for psychogenic polydipsia — a condition in which psychiatric disorders, such as schizophrenia, trigger compulsive water drinking.

“There have been cases where patients drank up to 15 liters of water a day. This can cause serious complications, especially without medical supervision,” the researcher emphasized.