Gigantism is a
disease (which may or may not be
genetic in origin) in which an
overactive pituitary gland produces too much
human growth hormone. The result is that a
person grows to an
extreme size. The disease is often accompanied by other
hormonal inbalances, causing
diabetes and other diseases.
These days, gigantism is treated by irradiating the pituitary gland to control its activity, together with hormone treatment to correct any remaining imbalances.
Before this treatment was found, the result of the disease was literally a giant, such as Robert Wadlow, the tallest man (of whom there is irrefutable evidence) who ever lived, who reached 8 feet 11 inches by his death at age 22. Many of the legends of giants throughout history were probably due to people afflicted with this disease.
Gigantism only results when the hormonal disorder occurs during childhood. If it begins in adulthood, acromegaly results.