States of both growth hormone deficiency and excess provide very visible testaments to the role of this hormone in normal physiology. Such disorders can reflect lesions in either the hypothalamus, the pituitary or in target cells. A deficiency state can result not only from a deficiency in production of the hormone, but in the target cell's response to the hormone.
Clinically, deficiency in growth hormone or defects in its binding to receptor are seen as growth retardation or dwarfism. The manifestation of growth hormone deficiency depends upon the age of onset of the disorder and can result from either heritable or acquired disease.
The effect of excessive secretion of growth hormone is also very dependent on the age of onset and is seen as two distinctive disorders:
1. Giantism is the result of excessive growth hormone secretion that begins in young children or adolescents. It is a very rare disorder, usually resulting from a tumor of somatotropes. One of the most famous giants was a man named Robert Wadlow. He weighed 8.5 pounds at birth, but by 5 years of age was 105 pounds and 5 feet 4 inches tall. Robert reached an adult weight of 490 pounds and 8 feet 11 inches in height. He died at age 22.
2. Acromegaly results from excessive secretion of growth hormone in adults, usually the result of benign pituitary tumors. The onset of this disorder is typically insideous, occurring over several years. Clinical signs of acromegaly include overgrowth of extremities, soft-tissue swelling, abnormalities in jaw structure and cardiac disease. The excessive growth hormone and IGF-I also lead to a number of metabolic derangements, including hyperglycemia.
Clinically, deficiency in growth hormone or defects in its binding to receptor are seen as growth retardation or dwarfism. The manifestation of growth hormone deficiency depends upon the age of onset of the disorder and can result from either heritable or acquired disease.
The effect of excessive secretion of growth hormone is also very dependent on the age of onset and is seen as two distinctive disorders:
1. Giantism is the result of excessive growth hormone secretion that begins in young children or adolescents. It is a very rare disorder, usually resulting from a tumor of somatotropes. One of the most famous giants was a man named Robert Wadlow. He weighed 8.5 pounds at birth, but by 5 years of age was 105 pounds and 5 feet 4 inches tall. Robert reached an adult weight of 490 pounds and 8 feet 11 inches in height. He died at age 22.
2. Acromegaly results from excessive secretion of growth hormone in adults, usually the result of benign pituitary tumors. The onset of this disorder is typically insideous, occurring over several years. Clinical signs of acromegaly include overgrowth of extremities, soft-tissue swelling, abnormalities in jaw structure and cardiac disease. The excessive growth hormone and IGF-I also lead to a number of metabolic derangements, including hyperglycemia.
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