The recent rash of allegations and admissions of Human Growth Hormone (HGH) use in Major League Baseball has brought this controversial substance into the limelight. And yet, most sports fans have a limited understanding of HGH and why it seems to be so prevalent in the modern sporting landscape.

Where to begin? Well, for starters, HGH is not a steroid. While it is widely understood and accepted that steroids increase muscle mass and improve athletic performance, there is a lack of scientific consensus on the benefits of HGH for athletes. What we do know about HGH is that it's medically approved for three purposes: stimulating growth in short children, reducing muscle wastage in AIDS patients, and correcting growth hormone deficiency in adults. It's illegal to possess and use HGH for any other reason.

So why do so many athletes seem to be using it?

"There are a number of theoretical benefits that haven't really been documented in humans," says Dr. Peter Tiidus, Chair of Kinesiology & Physical Education at Wilfrid Laurier University. "Theoretically, HGH will stimulate the release of another hormone-like substance called IGF-1, which is thought to be a stimulant of muscle growth and stimulates factors that contribute to muscle repair."

Tiidus specializes in the physiology of exercise-induced muscle damage and repair, and when you consider that athletes who admit to using HGH consistently claim that they used it to speed recovery from injuries, it might seem strange that there isn't more scientific documentation on the subject. Asked why the scientific community might shy away from this type of study, Tiidus suggests, "They don't want to encourage athletes to cheat."

If you're wondering why something that might help athletes recover more quickly from injuries would be banned, then you should consider some of the possible side effects of HGH use, which include irreversible acromegaly (abnormal growth of the hands, feet and face), high blood pressure, heart and liver damage, and arthritis. Most significantly, abnormally high levels of growth hormone in humans can cause dangerous growth in internal organs – including the heart. When Andre the Giant died in 1993 at the age of 46, it was a result of heart failure caused by a growth hormone-secreting pituitary tumour.

Another likely reason that pro athletes are turning to HGH instead of steroids is that none of the major pro sports leagues test for HGH in their players. The World Anti-Doping Agency (WADA) claims they have had a reliable blood test for HGH since 2003, but none of the players unions have been willing to approve the test for their sport.

So to sum up, HGH is a drug with no official proof of its effectiveness on athletes and no mass consensus on the likelihood of detection. Confused yet?

Don't be. Whether or not you want to call it cheating, athletes always have and always will do whatever it takes to give themselves an edge – real or perceived – on the competition. HGH is just the latest "training supplement" in the modern athlete's arsenal. It may not be as potent as steroids, but until Major League Baseball and their pro sports brethren are willing to enforce off-season, random blood testing on their players, HGH will continue to be an enticing option.

If WADA has its way, a commercially-available blood test for HGH will be on the market later this year. In spite of recent events, don't count on Major League Baseball being the first pro sport to adopt it in its testing procedures.

Next week: Why don't pro sports leagues test for HGH?

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