Nov. 20, 2008 -- They might not have exactly the same spring in their step as teenagers, but older folks taking an experimental once-a-day pill have roughly the same hormone levels as teenagers.
Hormones aren't the main point, however. The drug increases human growth hormone levels, which makes people grow taller, build muscle, and strengthen bones, among other myriad effects.
Researchers hope that the drug, MK-677, will improve the quality of life for older patients, who lose muscle mass as they age, limiting their independence and creating medical problems.
"We want to extend the time that people are healthy," said Michael Thorner, a doctor at the University of Virginia who lead the study. "It's clear that this drug won't be a substitute for good nutrition and exercise, but together this drug could have very beneficial effects."
MK-677, a Merck product, mimics the effects of ghrelin, a hormone produced naturally by the stomach that also stimulates the secretion of growth hormone from the pituitary gland.
Teenagers max out on levels of human growth hormone. After that levels steadily drop. By age 30 levels of human growth hormone have decreased by about 50 percent, and they continue to drop as we age.
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If the body doesn't produce enough growth hormone, either because of age or because of another problem, daily injections of growth hormone can cause a person to grow and develop more normally, but are expensive and painful. MK-677 could eventually replace the daily injections if proven to be safe.
As part of the effort to prove that MK-677 should be approved for patients, Thorner and his colleagues started out with 65 healthy patients between the ages of 60 and 81. They divided them into three groups. One-third took a placebo. Two-thirds were on MK-677. After the first year, everyone was put on MK-677.
After one year, the group on the placebo lost an average of just over one pound of weight. The group taking the MK-677 actually gained 2.2 pounds of muscle. Overall the two groups differed by about 3.3 pounds after one year. The study is ongoing.
That 3.3 extra pounds a year should provide additional support before a fall and extra cushioning during a fall. And if a patients takes the drug for many years, the accumulated muscle buildup would help improve the overall quality of life.
Just because a patient has more muscle doesn't mean they can use that muscle. The scientists proved that healthy older patients can regain, or at least, stave off, muscle loss. They didn't prove that patients on MK-677 could walk faster or lift more, the things that lead to a better life of greater independence or greater protection during a fall.
The beauty of MK-677, says Thorner, is that it's hard to abuse by those looking for an unnatural physical edge. MK-677 tops off what the body can naturally produce. If too much growth hormone is being produced the body senses it and shuts down production.
"This just restores levels back to what they were as a young adult," said Thorner. "It's impossible to overdose on it."
Other studies have shown that functional muscle mass in young patients who don't produce enough HGH naturally do have improve functional muscle mass, but it takes at least two years before a measurable effect is created.
Muscle mass, whether functional or not, wasn't the only effect of the drug. MK-677 also increases appetite, an additional benefit for older patients who tend to eat less as they age.
"One guy described it like he was a teenager again," said Thorner. "He went down to the freezer in the middle of the night and ate a quart of ice cream."
Patients on the drug also showed a slight increase in fasting blood glucose and were less sensitive to insulin, although these results were clinically insignificant. Bone density also decreased but was also clinically insignificant. Thorner expects, and other studies back him up, that longer use of MK-677 would create stronger bones than not taking the drug.
One limitation of the research for clinical purposes was that it was done in healthy adults, a point that Marc Blackman, a doctor and professor of medicine at John Hopkins' University made clear, and that Thorner agrees with.
Before the drug can be approved for older patients, or younger patients who don't produce enough growth hormone, more testing in unhealthy patients, the patients who would benefit most from MK-677, are needed.
"This is very exciting research," said Marc Blackman, a professor of medicine at John Hopkins' University who reviewed the research. "But it's not ready for clinical practice, it's not ready for prime time yet."
Related Links:
How Stuff Works: Human Growth Hormone
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