Growth hormone does not improve sports performance or increase muscle

Lead investigator and endocrinologist Professor Ken Ho said: “We were surprised to find that human growth hormone has no effect on muscle mass or sports performance
14 June 2007

New research on the effects and the detection of growth hormone doping at the Garvan Institute in Sydney takes the international sporting community one step closer to stamping out drug cheats.

Lead investigator and endocrinologist Professor Ken Ho said: “We were surprised to find that human growth hormone has no effect on muscle mass or sports performance. However, when taken with testosterone, it does have an effect, but cheats who use both drugs are much more easily caught with the promising new tests we have been evaluating”.

This is the first large-scale scientific study to evaluate the effects of human growth hormone taken alone and in combination with testosterone - a combination often used by sports drug cheats. The results of these studies have also helped develop a reliable doping test.

Human growth hormone is reported to be widely-abused by athletes who believe it boosts physical prowess. But the research study, led by Garvan Institute scientists, has discovered that contrary to popular belief, growth hormone taken by itself does not increase muscle mass or athletic performance. And they believe the performance-enhancing benefits are all in the mind.

The researchers recruited close to 100 young, recreational athletes for the study. They used a high, but safe dose of growth hormone and measured a number of performance aspects such as strength, power, and endurance. In addition, they kept knowledge about who was taking what from both participants and study assessors.

“While human growth hormone does increase body mass, the effect is due largely to fluid retention, not to increased muscle mass and, when taken on its own, we can not find any sports performance benefit; if it had a dramatic affect, we would have found it”, says Professor Ho.”

“However, when growth hormone was taken together with testosterone, there was an increase in muscle mass and one particular aspect of performance - sprint power,” But the combined drug regime enhances the sensitivity of our tests and means we can detect sports dopers for weeks after they stop taking the banned substances. This has major implications for random drug testing”, he added.

Co-investigator Dr Anne Nelson notes:” What is particularly interesting is that, when later questioned, half of the study participants wrongly thought that they were taking the active drugs, highlighting the power of wishful thinking. Hopefully, this evidence will deter the newly-emerging generation of athletes from taking hormones, which pose significant health risks, such as heart abnormalities and diabetes”.

“We hope that the new growth hormone doping test will soon be added to the worldwide repertoire of checks to remove athletes who don’t play fair from the competitive sporting arena, said Dr Nelson.

Notes to editors:

This research is being presented at ENDO 07, the annual meeting of the Endocrine Society, in Toronto, Canada (June 2 - June 5 2007).

A press briefing with Professor Ken Ho and Dr Anne Nelson has been scheduled for 9:30 am on June 3 at Metro Toronto Convention Centre.

The presentation titles of the relevant posters are: Growth Hormone and Testosterone Exert Differential and Additive Effects on Lean Body Mass in Recreational Athletes; Does Growth Hormone and Testosterone Supplementation Improve Physical Performance? A Double-Blind Placebo-Controlled Study in Recreational Athletes; and The Influence of Gender and Testosterone on the Response to GH of IGF Axis and Collagen Markers in Young Recreational Athletes: a Double-blind Placebo-controlled Study.

The Garvan Institute heads a consortium of five Australian and Japanese research groups that has been funded by the World Anti-Doping Agency (WADA) and the Australian Government Anti-Doping Research Program to develop a robust test for growth hormone doping.

The ethics approval for participation of human subjects in this study is from St Vincent’s Hospital HREC #H03/116.


The researchers randomly assigned the drugs to 97 participants all of whom were healthy young recreational athletes, with an average age of 28. The double-blinded, placebo-controlled study was carried out over eight weeks. Men were randomly assigned to receive growth hormone, testosterone, both drugs or placebo (an inactive substance). Women received either growth hormone or placebo. The athletes took up to four times the levels of growth hormone that the body produces naturally, which is much more than is used to treat medical conditions relating to growth hormone deficiency, but is still considered safe for an eight-week study.