Human Growth Hormone Doesn't Improve Athletic Performance

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That done, the researchers decided to weigh the evidence on growth hormone and athletic performance. "Other authors have questioned whether growth hormone improves athletic performance," Liu said.

This meta-analysis looked at 44 existing articles from 27 different study samples which included individuals aged 13 to 45. All were randomized, controlled trials, considered the highest level of evidence in medical science.

Taking human growth hormone resulted in an average increase of 2 kilograms in lean body mass, which could include muscle, but also water (growth hormone promotes water retention). This was considered statistically significant.

There was also a "borderline" significant increase in fat mass of about 1 kilogram.

There was, however, no improvement in aerobic endurance. "If anything, we found a hint of evidence that it actually may worsen your performance," Liu said.

Nor did people taking growth hormone increase their ability to lift things.

Two of three articles showed increased lactate levels, a factor which can actually hurt athletic performance.

And there were unwanted side effects.

"They're using small doses, and even then, there were adverse effects," said Mary Chavez, chairwoman and a professor of pharmacy practice at the Irma Lerma Rangel College of Pharmacy at Texas A&M Health Science Center, in Kingsville. "We need to be cautious, because even here, some of these people are getting into muscle tears and edema and fatigue. Nationally, there is a bill before Congress to make it a controlled substance, not just prescription-only."

Last December, a bill to make human growth hormone a controlled substance was submitted in both the Senate and the House; it is currently moving through the committee process.

More information

The Nemours Foundation has more on growth hormone in young people.