dwarfism(redirected from metatropic dwarfism)
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dwarfism,condition in which an animal or plant is less than normal in size and lacks the capacity for normal growth. Dwarfism is deliberately produced and perpetuated in certain species (e.g., in breeding miniature dogs and cultivating dwarf plants). Among humans, dwarfism usually results from a combination of genetic factors and endocrine malfunction. It can also be caused, however, by acquired conditions, such as kidney disease. Pituitary dwarfism is caused by an insufficiency of the pituitary growth hormonegrowth hormone
, glycoprotein hormone released by the anterior pituitary gland that is necessary for normal skeletal growth in humans (see protein).
..... Click the link for more information. (hypopituitary dwarfism). Typically, the pituitary dwarf stops growing in early childhood but retains normal body proportion, mental capacity, and sexual development. Pharmaceutical companies are cloning human growth hormone to stimulate growth in children afflicted with hypopituitary glands. This type of dwarf, who is completely normal except for size, is commonly called a midget. Cretinismcretinism
, condition produced in infants and children due to lack of thyroid hormone. It usually results from a congenital defect (e.g., absence of the thyroid, presence of only a rudimentary gland, inability of the gland to produce thyroxine).
..... Click the link for more information. is a type of dwarfism accompanied by mental retardation and distortion of the body, resulting from an insufficiency of thyroid hormone. Unlike cretinism and pituitary dwarfism (which are thought to be caused by a combination of heredity and endocrine malfunction), achondroplastic dwarfism is the result of a completely hereditary, dominant genetic trait. Typically, the growth of the limbs is stunted, but the size of the trunk and mental capacity are normal. Humans who range in height from 2 to 4 ft (5.08–10.16 cm) are generally classified as dwarfs. However, small size that is an inherited characteristic of race (such as among African Pygmies) is not considered to be dwarfism since the individuals in such groups are physiologically normal.
nanism, abnormal shortness (less than 130 cm for males and less than 120 cm for females).
The commonest cause of dwarfism is endocrine pathology. Dwarfism can be divided arbitrarily into proportional and dis-proportional (normal and achondroplastic) types. The former group includes pituitary, thyrogenic (cretin), and infantile dwarfism and dwarfism caused by brain disease, such as encephalitis and hydrocephaly. In pituitary dwarfism, which is caused by affection of the anterior lobe of the hypophysis (or the parts of the hypothalamus that regulate pituitary function) by tumor, infection, poisoning, or injury, the dwarf is almost normal mentally but the bodily proportions and size are those of a child, the gonads are underdeveloped, obesity is common, and the facial skin is wrinkled and senile. Thyrogenic (cretin) dwarfism, caused by affection of the thyroid gland, is accompanied by impairment of ossification, metabolic disturbances, dryness of skin, and mental retardation. Types of the disproportional category include rachitic dwarfism, caused by marked skeletal deformity, dwarfism in chondrodystrophy (congenital abnormality in cartilage formation), and dwarfism in systemic bone diseases.
Treatment (before body growth ceases) is aimed at eliminatingthe causes of the dwarfism; this sometimes involves substitutiontherapy. Dwarfism is characteristic of certain tribes in Africa(Pygmies), Asia, and Oceania.