MONDAY, Jan. 15 (HealthDay News) -- Human growth hormone is being sold in increasing amounts as a cure-all for the ravages of aging, but new research shows no evidence for these claims -- and even possible dangers from the treatments.

So concludes a study from Stanford University researchers reported in the Jan. 16 Annals of Internal Medicine.

Growth hormone is widely promoted on the Internet and its use as an anti-aging drug has been touted in media ranging from NBC's Today show to Business Week.

However, Dr. Marc Blackman, clinical director of the U.S. National Center for Complementary and Alternative Medicine, who was not involved in the new study, said: "I'm concerned this is a substantial and growing problem. In an aging society, wanting to age healthfully and well has included the use of this very powerful hormone, the effectiveness and safety of which are still under investigation and have not been proved for this purpose."

The negative side effects of growth hormone include joint swelling and pain, carpal tunnel syndrome and a trend toward an increased risk of diabetes or pre-diabetes, according to the study.

"Human growth hormone is not the fountain of youth," said the study's lead researcher, Dr. Hau Liu, a research fellow in the division of endocrinology at Stanford's Center for Primary Care and Outcomes Research.

Liu noted that as many as 30,000 people in the United States are taking growth hormone to try to stop the aging process. "They are spending anywhere from a few hundred to a few thousand dollars a month," he said. "They are spending this amount of money and getting only a slight, if any, benefit, but increasing the risk of serious side effects."

The researchers looked at 31 studies that included just 220 patients. "There is very little scientific evidence evaluating growth hormone for aging," Liu said. "This limited evidence suggests that there is very modest benefit and a potential for side effects."

Growth hormone caused small changes in body composition, such as a small gain in muscle mass and a small decrease in fat -- about 2 kilograms (4.4 pounds), Liu said. This is no more than you would get from moderate exercise, he noted.

However, there was a potential for some serious side effects, including, in men, the risk for abnormal breast development, Liu said. These side effects are reversible when one stops taking the hormone, he said.

Liu noted that growth hormone is not approved by the U.S. Food and Drug Administration for use as an anti-aging medication.

"If you want to increase your probability of living a long, healthy life, [then] eat right, get some exercise, get enough sleep. Those things probably increase your probability of living a long, fruitful life," Liu said.

One expert believes that growth hormone has no place as an anti-aging remedy and may come with dangers.

"The hucksters touting growth hormone as a magic bullet against aging claim that thousands of studies have been conducted on the hormone. Liu demonstrates definitively that this is not true -- only a handful of studies have ever been conducted using growth hormone in adults," said S. Jay Olshansky, a professor of public health and senior research scientist at the Center on Aging at the University of Illinois, Chicago.

Olshansky also accused people who dispense growth hormone of acting irresponsibly.

"If those running anti-aging or so-called longevity clinics continue to openly and brazenly administer growth hormone to their patients as an anti-aging intervention, they will not only be openly violating the law, they may very well be jeopardizing the health of their patients," he said. "This thorough analysis suggests that the time has arrived for the FDA and the U.S. Drug Enforcement Agency to crack down on this illegal and potentially harmful activity."

As men and women age, there is a progressive slow decline in the release of growth hormone, Blackman said. By the time people reach their late 60s or 70s, the reduction in the production of growth hormone is as much as 50 percent to 75 percent less than when they were in their 20s, he explained.

He noted that there are older people with a deficiency in growth hormone who can be successfully treated by replacing growth hormone. However, taking growth hormone to retard aging is not a proven therapy.

More information

Find out more about healthy aging at the U.S. National Institutes of Health.