Growth hormone is one of the hormones of the pituitary being capable of promoting growth, effecting directly or indirectly on somatic cells to stimulate overall protein synthesis in an animal body and stimulating release of free fatty acids to increase energy availability. Human growth hormone (HGH) plays a prominent role in protein metabolism and the regulation of growth. This is accomplished by accelerating the rate of transfer of amino acids from the extracellular to the intracellular compartment and incorporating the transferred amino acids into cell proteins. Deficiency in growth hormone results in a variety of medical disorders. In children, it causes dwarfism. In adults, the consequences of acquired GH deficiency include profound reduction in lean body mass and concomitant increase in total body fat, particularly in the truncal region.
The production of recombinant proteins allows a useful tool for the treatment of these conditions. GH replacement therapy is widely used in patients with growth deficiencies and provides satisfactory growth. Growth hormone replacement therapy is used in children to promote growth and in adults to improve muscle strength, reduce fat mass and improve metabolic profiles, which could predispose to cardiovascular disease. In contrast to the growth promoting effects of growth hormone, the metabolic effects have been less often studied, yet they may be very important to the risk-benefit assessment of HGH therapy in adults. Decreased skeletal and cardiac muscle mass and muscle strength lead to a significant reduction in exercise capacity. Bone density is also reduced. Administration of exogenous growth hormone has been shown to reverse many of the metabolic changes. Additional benefits of therapy have included reduction in LDL cholesterol and improved psychological well-being. Human growth hormone declines with age. HGH therapy, have been used for its effect on aging. HGH therapy has been shown to increase muscle mass and strength in elderly subjects. HGH therapy has also been used to treat diseases of the central nervous system such as Alzheimer's disease, Parkinson's disease, and senile dementia. Thus far, treatment with growth hormone and other hormone therapies in studying the effects of age and treating age-related illnesses has focused on pharmacological levels of treatment. HGH replacement therapy is widely used clinically, however, this therapy is associated several disadvantages: GH must be administered subcutaneously or intramuscularly once a day to three times a week for months, or usually years. GH therapy is known to counter insulin actions and is contra-indicated for individuals with diabetes mellitus. Insulin resistance and impaired glucose tolerance can occur. Accelerated bone epiphysis growth and closure has been observed in pediatric patients. |
|
