Two things cause diabetes insipidus. In some people, a part of the brain (called the hypothalamus) doesn't make enough antidiuretic hormone (called ADH), which your body needs to work right. In other people, the kidneys don't work with this hormone the way they should. Most people with diabetes insipidus get it after an injury to the head or after brain surgery. Some people with diabetes insipidus have a brain tumor. Sometimes it runs in families. Some medicines, like lithium, can also cause it. About 25% of the time, doctors can't find any reason for it.