Effects of Human Growth Hormones on Athletic Performance
Some athletes take human growth hormones (GH) in conjunction with testosterone (T) hoping to increase muscle mass and improve physical performance. But does it work?
Until recently, few studies have been done to see if GR alone or in combination works. An Australian and New Zealand research team recruited 103 recreational athletes 18-40, which included 63 men and 33 women with the average age of 27.9 years. Their objective was to see if GR alone or combined with testosterone improved body composition and performance. The results were published in the Annals of Internal Medicine, May 2010.
Men were randomly selected to receive GH, testosterone, placebo or a combination of GH and T and women were randomly selected to receive placebo or GH. Subjects were then measured on their power, strength, endurance and sprint capacities. Study results showed that GH “significantly reduced fat mass, increased lean body mass…and increased body cell mass in men when combined with testosterone.” In addition, GH improved sprint capacity in both men and women but not power, strength or endurance. Muscle mass was not increased when taking GH however, athletes did suffer from more joint pain and swelling while also retaining fluid
Limitations of the study included the fact that the dosages administered of growth hormone (2mg/d subcutaneously) and testosterone (250 mg/wk intramuscularly) may underrepresent the actual doses taken covertly by athletes and thus, the side effects would also be underrepresented.
Annals of Internal Medicine published a summary of this study in layman’s terms and is an excellent read. This version is printed below in its entirety.
Effects of Growth Hormone Doping on Athletic Performance
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What is the problem and what is known about it so far?
Growth hormone is naturally produced by the body and is important for growth and metabolism. Injectable growth hormone is available for use by people who have growth hormone deficiency. Many healthy athletes without growth hormone deficiency use the drug because they believe that it bulks up their muscles and improves their physical performance (growth hormone “doping”). However, no scientific research has shown that growth hormone improves physical performance.
Why did the researchers do this particular study?
To see whether growth hormone affects athletic performance.
Who was studied?
103 healthy recreational athletes aged 18 to 40 years who engaged in regular athletic training for at least 1 year.
How was the study done?
The researchers first measured physical fitness and the ability to pull a weight, jump, and sprint on a bicycle. They then assigned half of the group at random to receive either growth hormone or salt water injections for 8 weeks. At the same time, they assigned half of the men at random to also receive testosterone or salt water injections. They measured physical performance at the end of the 8-week period and again at 14 weeks after the athletes had stopped receiving the drug or salt water injections.
What did the researchers find?
Growth hormone increased the athletes’ ability to sprint on a bicycle but had no effects on fitness or their ability to pull a weight or jump. The effect on sprint capacity was nearly doubled in men who also received testosterone injections. Performance returned to normal 6 weeks after participants stopped receiving growth hormone and testosterone injections. Athletes who received growth hormone did not increase muscle mass but retained body fluid and had swelling and joint pain more often than those who received salt water injections.
What were the limitations of the study?
The investigators used lower doses of growth hormone than athletes are reported to use, and for a shorter time. Therefore, the drug’s effects on performance might be greater than in this study, and its side effects may be more serious. How the drug’s effects on performance might translate into competitive advantage for athletes is unclear.
What are the implications of the study?
Growth hormone injections seem to increase athletic sprinting when given alone or in combination with testosterone. The drug also causes a person to retain body fluid and have swelling and pain. This is the first demonstration of improvement in a particular aspect of physical performance with growth hormone, but if and how the findings translate into a competitive advantage for athletes is unclear.
Article and Author Information
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The summary below is from the full report titled “The Effects of Growth Hormone on Body Composition and Physical Performance in Recreational Athletes. A Randomized Trial.” It is in the 4 May 2010 issue of Annals of Internal Medicine(volume 152, pages 568-577). The authors are U. Meinhardt, A.E. Nelson, J.L. Hansen, V. Birzniece, D. Clifford, K.C. Leung, K. Graham, and K.K.Y. Ho.
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