MadSci Network: General Biology |
I’m sorry I haven’t answered your question Matthew but I have been on vacation and completely forgot to submit my answer before I left. You ask an interesting question concerning the use of growth hormone (also called somatotropin) to reverse aging. Growth hormone (GH) is one of several hormones released from the pituitary. The pituitary is a thumb-sized organ which is tethered to the brain by a narrow strand of tissue. It releases at least 8 different hormones into the blood stream, many of which control other endocrine glands (an endocrine gland is any organ which releases hormones into the bloodstream. A hormone is a chemical substance which is released by one cell, travels through the body, and affects the functioning of a separate distant cell) and therefore it is often referred to as the "master gland". GH acts directly on the long bones of the body, and the joints and muscles, causing them to grow during development. The absence of GH causes dwarfism, while too much GH causes giantism. Indeed, long term elevations in GH in adults cause a disorder known as acromegaly, in which the bones of the hands and face become thickened and distorted because the long bones are unable to grow. The idea of using GH to combat or reverse aging is due to two main observations. First, there is a decline in the amount of GH released by the pituitary during aging. Second, aging is often associated with osteoporosis (loss of bone mass), arthritis (inflammation of the joints), and loss of lean muscle mass. It has been reasoned that these changes in bone, joints, and muscle with age may be due to the loss of GH, and further, that replacing this GH in the elderly may reverse these effects. In addition, evidence of the ability of GH to build muscle mass in adults was seen in athletes how misused GH in order to enhance their strength and stamina. A couple of well publicized studies in the early 1990’s claimed that administration of GH to older men slowed the aging process. In these studies, the men who received GH had lower fat content, increased muscle mass, and increased bone mineral density. However, GH treatment also resulted in increased blood pressure and blood sugar. Subsequent controlled clinical studies in humans and studies using laboratory animals have had conflicting results. Today, research concerning GH and aging is going strong, but few scientists believe that GH therapy will have a major impact on aging. It is more likely that GH replacement therapy may be used in conjuncture with other life-style changes (i.e. change in diet, increased exercise, etc) to help reduce bone and muscle loss in the elderly. I would have to say that GH therapy will not reverse the aging process by 10 to 20 years (it certainly will not increase lifespan), but that low dose therapy might have some beneficial effects. I say low dose therapy because it should be pointed out that too much GH is probably worse than too little GH. Mice which have been genetically altered to make too much GH die sooner than normal mice, and show signs of accelerated aging. Also, Robert Wadlow, the worlds tallest recorded man, who was 8’11" died at the age of 22 from a minor injury because his immune system was altered due to his increased GH. If you are interested in reversing the aging process, the only proven method to increase lifespan in laboratory animals is dietary restriction. Significantly reducing the normal food intake of rats and mice (I cannot remember the actual amount but I think it is 40% - 60%) will increase their lifespan (again I think by 20% - 30%). There is some evidence that this may hold true for laboratory primates also. I, for one, however, do not practice this.
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