Gigantism or giantism, (from Greek gigas, gigantos "giant") is a condition characterized by excessive height growth. As a medical term, gigantism is rarely used except to refer to the rare condition of pituitary gigantism due to prepubertal growth hormone excess. There is no precise definition of the degree of tallness that qualifies a person to be termed a "giant." The term has been 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. more...
Typical adult heights of Americans and Europeans to whom the term might be applied are 210 - 240 cm (7 - 8 feet) though it may be possible for a person to grow up to 270 cm (9 feet) or taller. The term is rarely applied to basketball players and those whose heights appear to be the healthy result of normal genetics and nutrition.
Pituitary gigantism due to growth hormone excess is the single condition that accounts for nearly all cases of pathologic extreme height. The excess growth hormone usually results from oversecretion by a group of somatotrope cells of the anterior pituitary gland (termed a "somatotrope adenoma"). These cells do not respond to normal controls of growth or function. They grow very slowly, so that for many years the only effects of such an adenoma are the effects of excessive growth hormone.
The primary effect of growth hormone excess in childhood is excessive growth, but the tallness is accompanied by a characteristic physique recognizable to an endocrinologist. The typical physique involves heavy, thick bones, with large hands and feet and a heavy jaw. Once puberty is complete and adult height is achieved, continued thickening of the skin and growth of the jaw results in a combination of features referred to as acromegaly. Over decades, such an adenoma may reach a large enough size (2 cm or more in diameter) to cause headaches, impair vision, or damage other pituitary functions. Many years of growth-hormone excess can cause other problems as well.
If pituitary gigantism or acromegaly is suspected by a physician, the simplest diagnostic screening test is measurement of insulin-growth factor 1 in the blood. This is usually quite elevated but levels must be interpreted in relation to age and pubertal status. Additional confirmatory testing may include magnetic resonance imaging (MRI) of the pituitary to look for a visible adenoma, and suppressibility of growth hormone levels by glucose. Treatment depends on the size of the adenoma and may involve removal by a neurosurgeon, drugs such as octreotide or bromocriptine, or radiation. Treatment is discussed in more detail in the acromegaly article.
Childhood pituitary gigantism is a rare condition, and those affected are often unusual enough to attain a degree of celebrity status (e.g., André the Giant) Acromegaly is the term used for the condition of growth hormone excess when it occurs in adults. Acromegaly is a far more common disease in adults than pituitary gigantism is in children.
Other conditions of overgrowth or excessive tallness in childhood
Children who are excessively tall are often referred to pediatric endocrinologists for evaluation. The majority of children who seem excessively tall or large to their parents usually have a combination of simple familial tallness and childhood obesity.
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