News Release

Athletic benefit of growth hormone doping: Is it all in the athlete's mind?

Peer-Reviewed Publication

The Endocrine Society

If athletes believe they are using a performing-enhancing drug, they may think their athletic performance improves, and in some men it can, even if they are actually taking a dummy drug, a new study has found. Results of the study will be presented at The Endocrine Society's 90th Annual Meeting in San Francisco.

This so-called placebo effect was greater in male recreational athletes than in females, said lead author Jennifer Hansen, RN, a nurse researcher at the Garvan Institute of Medical Research in Sydney, Australia. In a study of growth hormone, the authors tested whether the power of the mind affects physical performance.

"Athletes are doping with growth hormone to improve sporting performance despite any evidence it actually improves performance," Hansen said. "Therefore, we wanted to know if any improvement in performance is due just to the athletes' belief that they are taking an agent that enhances performance, rather than to the agent itself."

Sixty-four young adult recreational athletes randomly received either growth hormone—a substance banned in sports—or an inactive substance (placebo) for 8 weeks. Neither the athletes who volunteered for the study nor the investigators knew which substance the athletes received. At the end of the study, the researchers asked the athletes to guess which agent they had taken and to say if they thought their sporting performance had changed. Then they tested the athletes on physical performance tests of endurance, strength, power, and sprint capacity.

Men were much more likely than women to think they had received growth hormone. Regardless of sex, athletes who took the dummy drug but believed they were on growth hormone ("incorrect guessers") thought their performance improved and actually had some improvement in all measures of performance. However, jump height (power) was the only test that showed a significantly greater improvement among the incorrect guessers, according to Hansen.

"The results of this study suggest that the placebo effect may be responsible, at least in part, for the perceived athletic benefit of doping with growth hormone for some people," Hansen said.


The study was funded by the World Anti-Doping Agency and the Australian Government Anti-Doping Research Program. Novo Nordisk supplied the growth hormone for this study.

Founded in 1916, The Endocrine Society is the world's oldest, largest, and most active organization devoted to research on hormones, and the clinical practice of endocrinology. Today, The Endocrine Society's membership consists of over 14,000 scientists, physicians, educators, nurses and students in more than 80 countries. Together, these members represent all basic, applied, and clinical interests in endocrinology. The Endocrine Society is based in Chevy Chase, Maryland. To learn more about the Society, and the field of endocrinology, visit our web site at

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