Growth Hormone Does Not Enhance Performance

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Main Category: Sports Medicine / Fitness
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Article Date: 18 Mar 2008 - 3:00 PDT

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A new study by researchers in the US found that contrary to what many people may assume, scientific evidence does not support claims that human growth hormone (HGH) increases strength or athletic performance.

The study was the work of Dr Hau Liu of the Santa Clara Valley Medical Center, San Jose, and Stanford University, California, and colleagues, and is published in the early online issue of the May 20th print edition of the Annals of Internal Medicine.

Liu and colleagues reviewed randomized controlled trials comparing HGH with non-HGH treatment in physically fit, healthy people aged 13 to 45 and found that while growth hormone increased lean body mass it did not increase strength and the capacity to exercise.

They also found that people who took GH had more frequent tissue swelling and experienced fatigue more often than people who did not take the substance.

The researchers concluded that the available scientific evidence does not support claims that GH improves physical performance. In fact while lean body mass may increase, strength does not and GH may even diminish exercise capacity and lead to other adverse side effects.

The safety and effectiveness of HGH is poorly understood, even though it is reportedly used to enhance athletic performance, said Liu and colleagues in their background to the study.

They decided to investigate all the published randomized controlled trials they could find that compared HGH with non-HGH treatments in healthy community dwelling people between 13 and 45 years of age. They searched a number of databases and found 44 articles of which 27 met their inclusion criteria.

When pooled together, the results showed that:

• 303 participants received HGH, equivalent to 13.3 person-years of treatment.


• The participants were young (mean age was 27 years), lean (mean BMI of 24), and physically fit (maximum O2 uptake was 51 mL per kilo of bodyweight per min).


• HGH dosage (mean of 36 micrograms per kg per day) and treatment duration (mean of 20 days) for studies where participants took HGH for more than a day varied.


• Lean body mass went up in participants taking HGH compared with those who did not (increase 2.1 kg, range 1.3 to 2.9), but strength and exercise capacity did not appear to increase.


• Lactate levels during exercise were significantly higher in 2 of the 3 studies that measured them.


• Participants who took HGH had soft tissue edema (swelling) and fatigue more often than non-HGH participants.

Liu and colleagues concluded that:

"Claims that growth hormone enhances physical performance are not supported by the scientific literature."

"Although the limited available evidence suggests that growth hormone increases lean body mass, it may not improve strength; in addition, it may worsen exercise capacity and increase adverse events," they added.

However, they said more research was needed to confirm these conclusions, and the study was limited by the fact that the dosages examined may not reflect what happens in real life.

HGH to improve athletic performance is often called sports doping, a practice that is banned by most professional sports organizations, including the International Olympic Committee, Major League Baseball, and the National Football League, said the researchers in their background information.

One of the reasons HGH is alleged to be so popular is because it is difficult to detect. It does not show in urine tests for example.

Last December, the 400-page Mitchell Report of former US Senator George Mitchell's 20-month investigation into illegal use of performance drugs in Major League Baseball, named 89 major baseball players who allegedly used performance drugs, some of whom have since admitted to using HGH, said Liu and colleagues.

"Systematic Review: The Effects of Growth Hormone on Athletic Performance."
H. Liu, D. M. Bravata, I. Olkin, A. Friedlander, V. Liu, B. Roberts, E. Bendavid, O. Saynina, S. R. Salpeter, A. M. Garber and A. R. Hoffman.
Ann Intern Med 2008; 60520-215.
20 May 2008, Volume 148 Issue 10

Click here for Article.

Click here for the Mitchell Report (PDF).

Sources: Annals of Internal Medicine press statement, journal article.

Written by: Catharine Paddock
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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