FRIDAY, Oct. 10, 2008 (HealthDay News) -- Adults who long for the vitality of their younger days may be curious about trying injections of human growth hormone, the same substance allegedly used by some Major League Baseball players to boost their athletic performance.

But can it really turn back the hands of time?

Studies of human growth hormone in healthy adults are limited. And what rigorous scientific evidence there is suggests that the risks -- and they can be substantial -- outweigh the benefits.

"I think people are looking for a pill or an injection or something that will cause them magically to become younger," said Dr. Hau Liu, associate chief of endocrinology and co-director of chronic care management at Valley Medical Center in San Jose, Calif. "At least from our view of the data, our conclusion is that it's not the fountain of youth."

Liu was lead author of an analysis of data culled from randomized, controlled trials of growth hormone use in healthy older adults. His team's study, published last year in the Annals of Internal Medicine, found an association between growth hormone use and slight changes in body composition, but no changes in other important health outcomes.

What's more, users of growth hormone had high rates of soft tissue swelling and joint pain, compared to people who didn't get these injections. There was also an increased risk of impaired blood sugar control or diabetes. Although this finding was not statistically significant, Liu suggests that it is "worrisome" given the epidemic rise of type 2 diabetes in the United States.

Human growth hormone is a protein made by the pituitary gland. It's important for normal development and maintenance of tissues and organs, and is especially important for normal growth during childhood, according to the U.S. National Institute on Aging.

As people enter their 40s, the amount of growth hormone produced starts to decline. And, despite a lack of solid evidence, some people believe that bolstering levels of the hormone through injections will help stave off the effects of aging.

In the United States, the U.S. Food and Drug Administration has approved the use of synthetic human growth hormone to treat children with short stature and some other growth problems caused by childhood diseases.

The FDA, however, prohibits drug companies from marketing growth hormone for "off-label" uses such as anti-aging. But that hasn't stopped some physicians from prescribing growth hormone to patients willing to pay the price.

It's estimated that some patients spend as much as $1,000 to $2,000 a month on growth hormone for anti-aging purposes, says the American College of Physicians.

"I suspect that the threat of legal action will be the only way this inappropriate use of growth hormone will be curbed," said Dr. Mary Lee Vance, a professor of internal medicine and neurosurgery at the University of Virginia Health System, who specializes in pituitary diseases.

Vance is concerned about the potential harm to patients. She once corresponded with a patient who took growth hormone ostensibly "to prevent aging." He died from a heart attack six months after starting the therapy, which someone else had prescribed, she said.

The American Association of Clinical Endocrinologists says there's currently no place for the use of growth hormone (GH) as an anti-aging agent. "The future role of GH therapy in various clinical conditions should be explored through appropriate scientific investigation and clinical verification," the association writes on its Web site.

Still, proponents of growth hormone therapy remain resolved. In April, a worldwide coalition of physicians and scientists in anti-aging medicine called on the U.S. Congress to reject proposed legislation that would classify human growth hormone as a Schedule III controlled substance, which would tighten restrictions on how it's dispensed.

Meanwhile, scientific investigation continues. Liu intends to expand his research to examine a combination of growth hormone with other agents. "There's some evidence that multiple agents somehow may have some synergistic effect on outcomes, and that's what we're trying to investigate further," he said.

But until those results are in, he suggests that the best life-extending advice comes from our mothers. "Exercise, eat well, don't smoke: Those are the therapies, really, that will help enhance your quality of life and increase your probability of living a long, healthy life," he said.

More information

For more on hormones and aging, visit the U.S. National Institutes of Health.

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