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gigantism

gigantism

[jahy-gan-tiz-uhm, ji-, jahy-gan-tiz-uhm]
gigantism, condition in which an animal or plant is far greater than normal in size. Plants are often deliberately bred to increase their size. However, among animals, gigantism is usually the result of hereditary and glandular disturbance. Among humans, gigantism is produced by an oversecretion of growth hormones by the acidophilic cells in the anterior lobe of the pituitary, causing excessive growth of all the tissues of the body. The metabolic rate is usually at least 20% above normal, which could be caused by an excess of the growth hormone alone, or oversecretion of the thyroid hormone in addition. Usually hyperglycemia (overactivity of the insulin-producing cells of the pancreas) is present. This condition eventually leads to degeneration of the islet cells, causing diabetes. Because of these metabolic abnormalities, the life expectancy of a giant is considerably less than normal. The treatment for gigantism is usually irradiation of the pituitary. The excessive height of the pituitary giant, which is defined at various levels above 7 ft (213 cm), is caused by excessive growth of the long bones. However, if the pituitary becomes overactive after growth is complete (marked by closure of the epiphyses of the long bones), the condition known as acromegaly results. Giants appear in the legends and folklore of many cultures.

Excessive growth, resulting from heredity, diet, or growth regulation disorder. Androgen deficiency causes long bones to continue growing after they would normally stop. Overproduction of growth hormone—usually due to a tumour—causes pituitary gigantism (see pituitary gland). With gradual but continuous growth, height may reach 8 ft (240 cm), with normal proportions. Greater susceptibility to infection, injury, and metabolic disorders shortens the life span. Surgery or radiation can be employed to curtail further growth. Gigantism often occurs with acromegaly.

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Gigantism or giantism, (from Greek gigas, gigantas "giant") is a condition characterized by excessive growth and height significantly above average.

Types

As a medical term, gigantism can refer to:

  • "Pituitary gigantism", which is due to prepubertal growth hormone excess. This is sometimes equated with acromegaly, but more precisely, an excess of growth hormone leads to "pituitary gigantism" (vertical growth) if the epiphyseal plates have not yet closed, but it leads to "acromegaly" (lateral growth) if they have closed.
  • "Cerebral gigantism", also known as Sotos syndrome, which is due to a mutation in NSD1.

Terminology

There is no precise definition of the degree of height 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. Typical adult heights of Americans of European descent to whom the term might be applied are 2.10 - 2.40 metres (7 - 8 feet). 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.

Other names somewhat obsolete for this pathology are hypersomia (Greek: hyper over the normal level; soma body) and somatomegaly (Greek; soma body, object pronoun somatos of the body; megas, megalos great).

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