Hormone may restore muscle in elderly.

Hormone may restore muscle in elderly

A preliminary study hints that a recombinant form of human growth hormone may boost muscle mass and skin thickness in some people over age 60 and perhaps improve their strength and endurance. However, scientists caution that the experimental treatment -- so far tested in only 12 men -- must undergo many more years of study before it can be declared effective or safe.

"These studies are very exciting," comments endocrinologist Mary Lee Vance of the University of Virginia in Charlottesville. But Vance advises against viewing human growth hormone as a potential cure for old age. "I just don't think you can make a global statement that this will improve everyone's life."

Human growth hormone, normally secreted by the pituitary gland, not only fuels children's growth but also helps promote leanness in adults by spurring cells to use stored fat for fuel. Scientists suspect that its production begins to taper off in many people after age 40, leading to some characteristic signs of aging, including increased fat deposition, decreased muscle mass and thinner skin.

"For many years it was thought that this progressive change in body composition was an inevitable consequence of aging," says Daniel Rudman of the Medical College of Wisconsin in Milwaukee. In the July 5 NEW ENGLAND JOURNAL OF MEDICINE, Rudman and his colleagues suggest that treatment with synthetic human growth hormone might help some older people counteract that steady decline.

The study involved 21 healthy men aged 61 to 81 who produced little or no growth hormone, as gauged by a marker in the blood called insulin-like growth factor I (IGF-I). All volunteers entered the study with deficient IGF-I blood levels of less than 350 units per liter. For six months, 12 of the men gave themselves subcutaneous injections of the synthetic hormone three times a week, while nine controls received neither treatment nor placebo. When therapy ended, the treated men had IGF-I levels of 500 to 1,500 units per liter -- a concentration common among people aged 30 or less. Controls showed no rise in IGF-I blood levels.

The treatment group also showed an 8.8 percent increase in lean body mass (which includes muscle), a 14.4 percent decline in fatty tissue and a 7.1 percent increase in skin thickness. The investigators measured bone density before and after therapy, but Rudman says the study provided no conclusive results on whether the treatment built stronger bones. Nor can the researchers tell whether the skin and muscle changes will last.

Their hope is that growth hormone can strengthen muscle and perhaps bone enough to help elderly people avoid bone-breaking falls, which frequently result in disability and loss of independence, Rudman says. Although men taking the hormone said they felt more energetic after treatment, the researchers note that such self-reports are subjective and possibly biased. In addition, the team has yet to prove that a leaner body mass means improved strength. Rudman hopes to establish that connection in future studies.

Even if further research verifies that the experimental therapy can benefit the elderly, physicians and patients must treat this drug with extreme caution, Vance warns in an editorial accompanying the research report. "It's a double-edged hormone," she told SCIENCE NEWS, noting that extended treatment or large doses can lead to high blood pressure, diabetes and even heart disease. Rudman adds that some older people don't have deficits in growth hormone and thus wouldn't be eligible for the treatment.

Jeremy Rifkin of Washington, D.C., a vocal critic of recombinant DNA technology, says he worries that reports like Rudman's may inadvertently boost illegal use of the synthetic hormone, which is already abused by athletes and bodybuilders. The FDA has approved the drug only for very short children who completely lack the natural growth hormone, Rudman notes.