Bio-identical Hormones and Aging
In 1989, at Veterans Administration hospitals in Milwaukee and Chicago, a small group of men aged 60 and over began receiving bio-identical hormone injections three times a week that dramatically reversed some signs of aging. The injections increased their lean body (and presumably muscle) mass, reduced excess fat, and thickened skin. When the injections stopped, the men's new strength ebbed and signs of aging returned.
Declining levels of these chemical messengers may trigger some aging processes. What the men were taking was bio-identical recombinant human growth hormone (rHGH), a synthetic version of the hormone that is produced in the pituitary gland and plays a critical part in normal childhood growth and development. Now researchers are learning that GH, or the decline of GH, seems also to play a role in the aging process in at least some individuals.
The idea that hormones are linked to aging is not new. We have long known that some hormones decline with age. Human growth hormone levels decrease in about half of all adults with the passage of time. Production of the sex hormones estrogen and testosterone tends to fall off. Hormones with less familiar names, like melatonin and thymosin, are also not as abundant in older as in younger adults. Bio-identical hormone replacement clearly show profound results in aging humans.
Hormones and Research on Aging
Produced by glands, organs, and tissues, hormones are the body's chemical messengers, flowing through the blood stream and searching out cells fitted with special receptors. Each receptor, like a lock, can be opened by the specific hormone that fits it and also, to a lesser extent, by closely related hormones. Here are some of the hormones and other growth factors of special interest to gerontologists that bio-identical hormone replacement shows amazing results.
Estrogen. The female hormone, estrogen is used in bio-identical hormone replacement therapy to relieve discomforts of menopause. Produced mainly by the ovaries, it slows the bone thinning that accompanies aging and may help prevent frailty and disability. After menopause, fat tissue is the major source of a weaker form of estrogen than that produced by the ovaries.
Growth Hormone. This product of the pituitary gland appears to play a role in body composition and muscle and bone strength. It is released through the action of another trophic factor called growth hormone releasing hormone, which is produced in the brain. It works by stimulating the production of insulin-like growth factor, which comes mainly from the liver. All three are being studied for their potential to strengthen muscle and bones and prevent frailty among older people. Thousands of studies have been done using bio-identical hormone replacement therapy with rHGH
Melatonin. This hormone from the pineal gland responds to light and seems to regulate various seasonal changes in the body. As it declines during aging, it may trigger changes throughout the endocrine system.
Testosterone. The male hormone, testosterone is produced in the testes and may decline with age, though less frequently or significantly than estrogen in women. Researchers are investigating its ability to strengthen muscles and prevent frailty and disability in older men when administered as testosterone therapy. This hormone requires a delicate balance using bio-identical hormone replacement therapy with testosterone. Too little, ineffective. Too much and we see potential side effects, which may include an increased risk of certain cancers, particularly prostate cancer. Just right and we respond profoundly.
DHEA. Short for dehydroepiandrosterone, DHEA is produced in the adrenal glands. It is a weak male hormone and a precursor to some other hormones, including testosterone and estrogen. DHEA is being studied for its possible effects on selected aspects of aging, including immune system decline, and its potential to prevent certain chronic diseases, like cancer and multiple sclerosis.
Bio-identical hormone replacement therapy
We also know that when some declining hormones are replaced, various signs of aging diminish. Most, like growth hormone, are still in the experimental stage, but one, estrogen, is used in medical practice to alleviate the discomforts of menopause. Bio-identical hormone replacement therapy with estrogen also lessens the accelerated bone loss that comes with menopause and may help prevent cardiovascular disease. Preliminary studies suggest that testosterone replacement may likewise have benefits for aging men, by increasing bone and muscle mass and strength. However, questions about cancer and other risks surround both estrogen and testosterone replacement therapy and have not yet been resolved.
A hormone that has attracted the interest of many researchers is DHEA (short for dehydroepiandrosterone), which is abundant in youth but begins to decline in humans at about age 30. Very low levels of DHEA have been linked to cardiovascular disease in men, some cancers, trauma, and stress; low levels are also associated with old age, particularly in the unwell, institutionalized elderly. In animal studies, replacing DHEA has had startling anti-aging effects. Large doses of the hormone have restored older animals' strength and vigor.
How DHEA works is still not clear. Circulating through the blood stream in an inactive form, called DHEA sulfate, this hormone becomes active when it comes in contact with a specific cell or tissue that "needs" it. When this happens, the sulfate is removed.
DHEA seems to be needed, for example, to assist in the function and proliferation of immune cells. In experiments with mice, DHEA sulfate boosted the older animals' levels of a substance called interleukin-2, important in the immune response. There is now evidence that too much DHEA can be harmful.
Hormones are aided and abetted by an arsenal of other substances that also stimulate or modulate cell activities. Known collectively as growth or trophic factors, these include substances such as insulin-like growth factor (IGF-1), which mediates many of the actions of GH. Another trophic factor of interest to gerontologists is growth hormone releasing hormone, which stimulates the release of GH.
The mechanisms -- how hormones and growth factors produce their effects -- are still a matter of intense speculation and study. Scientists know that these chemical messengers selectively stimulate cell activities which in turn affect critical events, such as the size and functioning of skeletal muscle. However, the pathway from hormone to muscle is complex and still unclear.
Consider growth hormone. It begins to stimulating production of insulin-like growth factor. Produced primarily in the liver, IGF-1 enters and flows through the blood stream, seeking out special IGF-1 receptors on the surface of various cells, including muscle cells. Through these receptors it signals the muscle cells to increase in size and number, perhaps by stimulating their genes to produce more of special, muscle-specific proteins. Also involved at some point in this process are one or more of the six known proteins that bind with IGF-1; their regulatory roles are still a mystery.
As if the cellular complexities weren't enough, the action of growth hormone also may be intertwined with a cluster of other factors -- exercise, for example, which stimulates a certain amount of GH secretion on its own, and obesity, which depresses production of GH. Even the way fat is distributed in the body may make a difference; lower levels of GH have been linked to excess abdominal fat but not to lower body fat.
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