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growth hormoneSee also auxins (plant growth hormones).
Role in Dwarfism and GigantismA deficiency of growth hormone secretion before puberty (by the end of which the synthesis of new bone tissue is complete) results in pituitary dwarfism. Pituitary dwarfs, who can be as little as 3 to 4 ft (91–122 cm) tall, are generally well proportioned except for the head, which may be relatively large when compared to the body (this relationship of head to body is similar to that of normal children). Unlike cretins, whose dwarfism is caused by a deficiency of thyroxine, pituitary dwarfs are not mentally retarded; they are often sexually immature. They can be treated by injections of synthetic growth hormone, either somatrem or somatropin, which are produced by genetically engineered bacteria.
An excess of growth hormone in children results in gigantism; these children grow to be over 7 ft (213 cm) in height and have disproportionately long limbs. Excess growth hormone produced after puberty has little effect on the growth of the skeleton, but it results in a disease affecting terminal skeletal structures known as acromegaly.
Other Medical UsesHGH has been used with some success to combat the weight loss and general wasting characteristic of AIDS and cancer. It is used illegally by bodybuilders and athletes to increase muscle mass. Controversy surrounds its use in normal children who simply want to be taller. In addition, a 1990 medical study that reported the reversal of many of the physiological effects of aging with regular injections of HGH has created a lucrative black market for it and has prompted funding of further trials. There has been no conclusive evidence, however, to support the use of HGH as an anti-aging treatment, and it can cause serious side effects, including diabetes, in older adults.
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- hormone
Hormone, secretory substance carried from one gland or organ of the body via the bloodstream to more or less specific tissues, where it exerts some influence upon the metabolism of the target ...
- gonadotropic hormone
Gonadotropic hormone or gonadotropin, any one of three glycoprotein (see protein) hormones released by either the anterior pituitary gland or the placenta (the organ in which maternal and feta...
- acromegaly
Acromegaly, adult endocrine disorder resulting from hypersecretion of growth hormone produced by the pituitary gland. Since the bones cannot increase in length after full growth is attained, t...
- thyroid gland
Thyroid gland, endocrine gland, situated in the neck, that secretes hormones necessary for growth and proper metabolism. It consists of two lobes connected by a narrow segment called the isthm...
- gigantism
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...
- auxin
Auxin, plant hormone that regulates the amount, type, and direction of plant growth. Auxins include both naturally occurring substances and related synthetic compounds that have similar effect...
- dwarfism
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....
- pituitary gland
Pituitary gland, small oval endocrine gland that lies at the base of the brain. It is sometimes called the master gland of the body because all the other endocrine glands depend on its secreti...
- gall, in botany
Gall, abnormal growth, or hypertrophy, of plant tissue produced by chemical or mechanical (e.g., the rubbing together of two branches) irritants or hormones. Chemical irritants are released by...
- cyclosis
Cyclosis, streaming of cytoplasm within a living cell without deformation of the external cell membrane. In some plant cells there is a rapid rotatory cytoplasmic movement, which is limited to...
