Gigantism, also known as giantism , 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 persons between 7 and 9 feet 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 all 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 and somatomegaly . In the past, while many of them were social outcasts because of their height, some found employment in Friedrich Wilhelm Is famous Potsdam Giants regiment. (source : wikipedia)