Growth Hormones Retain Seniors' Muscles
Study Shows MK-677 Increases Muscle Mass That Normally Declines With Aging
Nov. 3, 2008 -- A daily dose of an oral drug that stimulates release of growth hormone helps retain muscle in healthy older adults, reversing part of the normal aging process, a new study shows.
Researchers at the University of Virginia conducted a two-year study of 65 healthy older adults, giving some an oral ghrelin mimetic, or MK-677, and others a placebo.
Volunteers between 60 and 81 who received MK-677, a drug provided by Merck Research Laboratories, experienced increased growth hormone levels to those seen in young adults.
Michael Thorner, MB, BS, DSc, and Ralf Nass, MD, of the University of Virginia, tell WebMD that blood sugar increased in people taking the new drug, and the body's sensitivity to insulin decreased slightly.
"This is an expected effect of enhancing growth hormone secretion. The changes are very mild and are unlikely to be of clinical significance in subjects who are not diabetic," Thorner says.
The purpose of the study, published in the November issue of Annals of Internal Medicine, was to determine whether stimulating growth hormone altered body composition -- and it did, Thorner tells WebMD.
"They also gained muscle mass in the limbs, which declines in the normal aging process," Thorner says. "On MK-677, they didn't lose any muscle mass. The limb fat increased as well. Appetite was enhanced. We were very surprised."
Body Weight and Body Fat
At 12 months, body weight increased 1.76 pounds in the placebo group vs. 5.95 pounds in those taking the test drug. Total body fat did not differ significantly. Quality-of-life measures also did not differ significantly between the two groups.
"We found a mild decrease of LDL, the bad cholesterol," Nass says. "There was a mild decrease in insulin sensitivity. But allowing muscle mass to increase is a positive effect."
The side effects were not significant, Thorner says, with the most frequent being minor swelling in the feet, ankles, and legs, temporary muscle pain, and increased appetite.
Nass says the goal of researchers is to determine definitively "whether there are some interventions that could help with some aspects of the aging process."