A man whose finger bones looked mysteriously "eaten away" on an X-ray was actually a textbook case for doctors who have seen what high levels of a hormone called parathyroid hormone can do to the body, the Fox News reported.

The 45-year-old patient in Japan had a noncancerous tumor on his parathyroid glands, which are four tiny glands that sit adjacent to the thyroid gland in the throat. The tumor was causing the glands to be overactive, and produce too much parathyroid hormone, which controls calcium levels in the body.

The man's high levels of the parathyroid hormone had led to an acceleration of the normal breakdown of his bones, resulting in shrinking finger bones. When doctors removed his tumor, the man's hormone levels quickly returned to normal, according to a report of his case published May 21 in the New England Journal of Medicine.

Cases of overactive parathyroid glands that are as severe as this man's case are rarely seen nowadays.

It's rare for a tumor on the parathyroid glands to grow so large, said Dr. Bart Clarke, an endocrinologist at the Mayo Clinic in Rochester, Minnesota, who wasn't involved with the case.