Proving that the drug will have sufficient benefits to warrant FDA approval may be difficult. Small gains in physical functioning would not qualify, and tests on many thousands of people would be needed in the future -- hurdles that drug companies are now reluctant to face.

The researchers found that stimulating hormone production improved physical functioning in older people. After taking the drug, they were able to walk faster and with better balance and to climb stairs faster, among other things.

"In general, people on the drug had a lot more energy, they had more get up and go," said Dr. George Merriam, a University of Washington professor of medicine and physician for the VA Puget Sound Health Care System.

Participants in the study, ages 65 to 84, also had increased muscle mass after taking the drug.

Merriam presented the research findings Wednesday at the International Congress of Neuroendocrinology in Pittsburgh.

Regulates Metabolism and Body Composition

Growth hormone is naturally produced by the pituitary gland to regulate growth and is especially vital during childhood and puberty. It continues to regulate metabolism and body composition through life, but production drops by half by middle age and 70 percent or more in old age.

About 10 million people in the US age 65 and older now need assistance with at least one daily living activity such as walking, dressing, bathing, using the toilet, eating and getting out of a bed or chair, according to the National Center for Health Statistics. That ranges from about 11 percent of those 65 to 79, to more than half of those over 85.

Nearly 400 men and women with relatively mild physical problems participated in the research by scientists at the University of Washington, four other universities and Pfizer.

They were eligible if they had fallen at least twice in the past year, had lost grip strength or had trouble with tasks such as errands, cooking, making the bed, dressing or putting away groceries.

Encouraging, Not Revolutionary

Participants were given a placebo or a tablet form of a "growth hormone secretagogue" (GHS), which stimulates growth-hormone production.

Over the six to 12 months of the study by the scientists, participants who received the drug were able to walk faster heel-to-toe, such as required in a sobriety test, and climb stairs faster. One other study with the drug has shown physical improvement after injections of the drug. Others studies have shown participants could stabilize physical function, but not improve it.

Patients in the University of Washington study receiving the drug also averaged an increase of about 3 pounds in muscle mass. And blood tests showed their growth hormones reached higher levels each day than those who received the placebo. Some patients had side effects of insomnia and increased blood sugar.

Merriam said the improvements didn't revolutionize the participants' lives. But the results are encouraging, he said.

"The results suggest that GHS treatment has promise in prolonging the capacity for independent living, but I can't say we're there yet," Merriam said.

Natural Production

Growth-hormone injections have long been given to children who have deficiencies of the hormone. Some have also promoted them as anti-aging treatments, despite limited scientific evidence of their effectiveness. And some athletes have abused the hormone in hopes of improving their performance.

Side effects of the injections can include swelled feet and legs, abnormal joint growth, arthritis-like symptoms, high blood pressure, muscle pain, headaches and bloating.

Merriam said use of GHS, which promotes natural growth-hormone production, is a better approach because the pituitary will stop production when the body has enough. "You have a checks-and-balance system," he said.

FDA Approval in Doubt

But Merriam said proving that the drug will have sufficient benefits to warrant approval by the federal Food and Drug Administration would be difficult at this stage. Small gains in physical functioning would not qualify, he said, and tests on many thousands of people would be needed in the future -- hurdles that drug companies are now reluctant to face, he said.

Pfizer, which financed the University of Washington study, earlier investigated marketing the GHS tablets as a "frailty" drug.

But the company discontinued the research because the FDA indicated it would have to show improvement on many levels to treat such a broad-reaching condition. Now Pfizer is searching for other, smaller-scale problems that it might help.

Other institutions participating in the research were Stanford University, Johns Hopkins University, University of Arkansas and Duke University.

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