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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