Healthy living
Anti-ageing
Growth hormone boosts muscle mass in older people
The words 'old' and 'frail' often go hand in hand but new research into a drug that increases levels of growth hormone and boosts muscle mass could help make the association a thing of the past
Growth hormone levels in the body are highest during puberty but as we age levels of the hormone decrease. The decline may be an important factor in why older people begin to grow frail, losing vital reserves of fat and muscle. Researchers at the University of Virginia Health System (UVa) tested an experimental drug called MK-677 that stimulates the release of growth hormone on a small group of healthy older people and found that it boosted muscle mass by an average of 20 per cent.
"Frailty is one of the scourges of elderly persons, and as researchers are beginning to learn about its causes, they are asking whether growth hormone deficiency is one of them," says Dr Michael Thorner, who led the research.
Sixty five healthy men and women, aged 60 to 81, took part in the two-year study. For the first year, half the participants were given a single daily dose of MK-677 while the other half were given a placebo. In the second year, those on the placebo started taking MK-677 while the first MK-677 group were randomly assigned to either continue taking the drug or receive a placebo instead.
The researchers measured a wide range of variables at the start of the study and again at six-month intervals to see whether the drug would significantly change body composition. These included body weight, fat and muscle mass, insulin sensitivity and bone density. Participants were also made to complete timed walks and other exercises to assess their muscle strength and function.
The drug was able to restore levels of growth hormone to those found in young, healthy adults. Those taking MK-677 increased their body weight by an average of 2.7kg compared with just 0.8kg in the placebo group. 'Fat-free mass' - mostly made up of muscle - increased significantly in the MK-677 group but decreased in the group taking the placebo. According to researchers, the drug restored 20 per cent of muscle mass loss associated with normal ageing.
The effects of the drug were maintained for those taking it for the full two years and went away in those who stopped taking it after the first year. Similarly, those who started taking the drug in the second year experienced the same effects as the group who took it in the first year.
Although the drug showed positive results for boosting muscle mass and body weight, researchers did report a small increase in blood sugar levels in those taking the drug as well as a reduced sensitivity to insulin – a possible precursor to diabetes. Interestingly, while there was an increase in muscle mass, the strength and function of the muscles weren't enhanced. 'This finding is probably because the participants were already fit before they started,' explains Dr Thorner. 'It is also known that even in young subjects growth hormone has to be given for several years before an increase in strength is recorded.'
This isn't the first time growth hormone has been shown to affect muscle mass: 'Previous pioneering studies have shown that growth hormone secretion and muscle mass both decline progressively from mid-puberty and that they appear to be correlated,' says Dr Thorner. However, it is the first study to use the drug MK-677 to stimulate growth hormone secretion.
The trial was too small to draw any definite conclusions and, after only two years, not long enough to find out if the drug could carry any long-term risks. However, Dr Thorner warns that even if a treatment for 'frailty' became a reality in the future, it wouldn't work on its own; 'Staying active, doing regular exercise and eating a nutritious diet are all needed to maintain muscle mass into old age and these will be required even if this or a similar compound became available.'
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Information on this site is for interest only and is not a substitute for professional medical advice. You should consult your own doctor about any specific health concerns.
