Athletes who take human growth hormone may not be getting the boost they expected.
"It doesn't look like it helps, and there's a hint of evidence it may worsen athletic performance," said Dr. Hau Liu, of
Growth hormone, or HGH, is among the performance enhancers baseball stars Roger Clemens and Andy Pettitte were accused of taking in the blockbuster Mitchell Report. Clemens denies using the hormone, while Pettitte admits using it.
But the new research has some limitations and sheds no light on long-term use of HGH. The scientists note their analysis included few studies that measured performance. The tests also probably don't reflect the dose and frequency practiced by athletes illegally using the hormone. Experiments such as that aren't likely to be conducted.
"It's dangerous, unethical, and it's never going to be done," said Dr. Gary I. Wadler, a member of the World Anti-Doping Agency and a spokesman for the
Human growth hormone is made by the pituitary gland and promotes growth. A synthetic version has been available since the 1980s and its use is restricted for certain conditions in children and adults, including short stature, growth hormone deficiency and wasting from AIDS.
Although banned for other uses, growth hormone has been used by a variety of athletes and was cited along with steroids as one of the performance-enhancing drugs abused by baseball players in the report in December by former Senate majority leader George Mitchell. Several athletes, including Pettitte, have said they used HGH while recovering from an injury, an issue not covered in the review.
"There are a lot of claims that it's this wonder drug," said Liu.
Wadler said one of the appeals of growth hormone for athletes is that it can't be detected in a urine test. A blood test will be available soon, and another is in development, he said. "They think they are getting a free ride they aren't getting a drug test," he said. "They believe they are stronger and bigger."
Liu and his colleagues at
Researchers found that those who got the hormone put on about five pounds more of muscle, and lost about two pounds more of fat, although the fat loss wasn't statistically different. The researchers said some of the extra body mass could just be fluid buildup. There was no difference found in strength or exercise stamina between the two groups, but there were only two strength studies and eight that measured exercise. Those who got the hormone had more side effects including swelling and fatigue. The review couldn't consider long-term effects, since the longest study was three months, and most were much shorter.
The researchers also said the doses used in the research may be lower than those used by athletes, who may be combining growth hormone with other performance-enhancing drugs.
Dr. Alan Rogol of the