In the quest for youth, many look to human growth hormone (HGH) as a miracle elixir.
Numerous books have touted its benefits as an anti-aging therapy, and a casual Internet search brings up dozens of sites pointing to its efficacy at staving off age-related changes in the body.
However, a recent review of published studies suggests that HGH provides few of the touted benefits for adults who are healthy. Worse, the side effects could mean that regular users are putting their health in jeopardy.
The review is published in the current issue of the medical journal Annals of Internal Medicine.
"The findings suggest that if someone is taking growth hormone to prevent or reverse aging, they should give it a second thought," said lead researcher Dr. Hau Liu of Stanford University.
"This review suggests that there are modest or even minimal benefits associated with growth hormone, and HGH could be associated with significant side effects, including a trend toward diabetes and pre-diabetic conditions."
Other medical experts who use HGH in their practices say the review sends an important message to consumers about the potential dangers of unapproved use of the hormone.
"This review doesn't tell any of us who work in the field anything at all new," said Dr. Mary Lee Vance, professor of medicine at the University of Virginia Health Sciences Center in Charlottesville. "But I think it is particularly important for those in the medical community and anyone else."
The very fact that HGH is a problem at all may be surprising to some. But today, it is illegal to distribute HGH as an anti-aging therapy in the United States.
Despite this, previous research has estimated that between 20,000 and 30,000 healthy American adults used growth hormone shots as an anti-aging therapy in 2004.
It is a situation that some say amounts to abuse of an otherwise useful therapy.
"I'm not against the use of growth hormone," Vance said. "I prescribe a lot of human growth hormone myself, but for people who are deficient in it because of disease."
Off-Label HGH Prescriptions Costly, Possibly Dangerous
Liu says most healthy adults who obtain HGH probably do so either online or through their doctors. Though use may be relatively common, he says the off-label prescription of HGH is particularly troubling.
"Growth hormone is an FDA-approved drug with FDA-approved indications," Liu said. "Definitely, it is beneficial in certain conditions -- children and adults with specific diseases."
For those without these specific conditions, however, a daily dose of HGH could cause much more harm than good, Vance says.
"For a physician to prescribe human growth hormone off-label for a patient for whom it is not indicated raises some real questions," she said. "First of all, it has not been approved and it has not been shown to be beneficial for healthy adults, and of course, it does have side effects."
Some of these side effects include swelling, carpal tunnel syndrome, and the formation of breasts in men -- a condition known as gynecomastia.
Research has also suggested that regular use of HGH in healthy adults can lead to diabetes and pre-diabetic conditions.
Cost is also a factor. Liu says that many people who use HGH off-label can end up paying thousands of dollars per year.
"People are paying quite a bit for these growth hormone shots," Liu said.
Anti-Aging Proponents Say Review Incomplete
Proponents of the use of HGH as an anti-aging therapy say that the study does not take all available research into account.
"The Liu et al paper is flawed, as it is based on an incomplete compilation of clinical studies of HGH replacement in healthy adults," said Dr. Ronald Klatz, president of the American Academy of Anti-Aging Medicine (A4M), in a statement issued Monday.
"The A4M submits that thousands of published studies on hundreds of thousands of patients have demonstrated the clear benefits of adult GH replacement therapy, when utilized under proper clinical guidelines and at proper physiological dosages."
Among these studies, the A4M maintains, are those showing that normal, healthy adults taking HGH experienced increases in lean muscle mass, decreases in fat mass, increases in bone density, and a host of other health benefits.
Liu's review showed that positive changes in body composition occurred with HGH use.
"We found examples of how fat mass decreased on average a little over 4.5 pounds, and lean body mass, or muscle, increased by about 4.5 pounds," Liu said.
"But we did not find any other clinically important outcomes that changed."
Vance says this relatively mild benefit is far outweighed by the potential for adverse side effects.
"When you're using a drug that costs that kind of money with the side effects that it has and the potential to cause the growth of cancer, I think that the risk outweighs this benefit," she said. "Even though body composition changes occur -- we expect that -- this has not been shown to translate into any functional benefit or longevity benefit."
"Changing body composition does nothing for cardiovascular fitness. Exercise and improved dietary regimens are much more beneficial."
Still, anti-aging proponents say that HGH supplementation is critical in aging adults -- particularly considering that levels of the hormone in the blood tend to decline with age.
"To deny the benefit of HGH and other essential hormonal regulators of metabolism in deficient patients based on age may be considered a heinous act of malpractice which will prove to be erroneous and shortsighted in the years to come," reads the A4M statement.
"In the future, the replacement of essential hormones that decline with age may be seen as important as insulin replacement in diabetics today."
Alternatives in the Fight against Aging
For those unwilling to pay for off-label HGH -- or risk its side effects -- there are a few old-fashioned anti-aging tips that can accomplish the same body composition changes seen with the hormone, Liu says.
"If you think about what people are paying, which is in the hundreds to thousands of dollars, if they were able to go out and exercise or get a personal trainer, they could probably attain those types of changes with regular exercise," he said.
"We should do the things that our moms and doctors tell us to do: Eat well. Exercise. Drink only moderately. Don't smoke, and get enough sleep."