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Gigantism, also known as giantism (from Greek γίγας gigas, "giant", plural γίγαντες gigantes), is a condition characterized by excessive growth and height significantly above average. In humans, this condition is caused by over-production of growth hormone in childhood resulting in people between 7 feet (2.13 m) and 9 feet (2.75 m) in height.
The term is typically applied to those whose height is not just in the upper 1% of the population but several standard deviations above mean for persons of the same sex, age, and ethnic ancestry. The term is seldom applied to those who are simply "tall" or "above average" whose heights appear to be the healthy result of normal genetics and nutrition. Gigantism is usually caused by a tumor on the pituitary gland of the brain. It causes growth of the hands, face, and feet. In some cases the condition can be passed on genetically through a mutated gene.
Other names somewhat obsolete for this pathology are hypersoma (Greek: hyper over the normal level; soma body) and somatomegaly (Greek; soma body, genitive somatos of the body; megas, gen. megalou great). In the past, while many of them were social outcasts because of their height, some (usually unintentionally) found employment in Friedrich Wilhelm I's famous Potsdam Giants regiment.
Many of those who have been identified with gigantism have suffered from multiple health issues involving their circulatory or skeletal system.
Hypersecretion of growth hormone causes gigantism in children and acromegaly in adults. Evaluation of growth hormone hypersecretion cannot be excluded with a single normal GH level due to diurnal variation. However, a random blood sample showing markedly elevated GH is adequate for diagnosis of GH hypersecretion. Additionally, a high-normal GH level that fails to suppress with administration of glucose is also sufficient for a diagnosis of GH hypersecretion.
Insulin-like Growth Factor-1 (IGF-1) is an excellent test for evaluation of GH hypersecretion. It does not undergo diurnal variation and will thus be consistently elevated in GH hypersecretion and therefore patients with gigantism. A single normal IGF-1 value will reliably exclude GH hypersecretion.
Reports of gigantism exist throughout history, with some nations and tribes taller than others. The giants of Crete are listed in various historic sources, beginning with Titan, a Greek mythological giant, and including Gigantus, after whom giants and gigantism are named. Rhodes is another island where giants were said to have lived, with the Colossus of Rhodes, a giant statue of a giant patron god Helios. Goliath, a giant mentioned in the Bible, was a Philistine warrior who was killed by David in a battle between the Israelites and the Philistines. A member of Goliath's family is also recorded as having six fingers on each hand and six toes on each foot.