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Sometime in late September or early October, the NFL will begin testing players for using human growth hormone as a performance-enhancing drug.

But if you're thinking the first round of tests will catch or scare off HGH users in the NFL, well, don't bet on it.

When news broke last week that the NFL and its players union agreed to HGH testing, my first thought was how it would affect this season. There's been no testing for HGH, so there's reason to suspect a meaningful percentage of players are using it. And anyone testing positive when the tests begin will be suspended the mandatory four games for a first-time violation.

"I think there's a good number of guys that are probably on it, if I had to guess," said Packers guard Josh Sitton. "It will be interesting to see."

But the more you research HGH testing, the less you think there will be many positive tests. In fact, odds are pretty good there won't be any. That doesn't mean players aren't using it. It just means catching them is difficult, and that the agreement between the league and players union to use the current incarnation of HGH testing is just a foot in the door. Whether they walk through as the tests improve, we'll see.

First, though, let's take a quick look at why HGH is on the banned list of PEDs in the Olympics, Major League Baseball and now the NFL, among other sports.

HGH is a naturally occurring hormone produced by the pituitary gland that promotes the growth of bone and tissue such as muscles. A synthetic version has been available since the early 1980s and is used to treat medical conditions such as growth hormone deficiency and wasting from AIDS.

Athletes and anti-aging enthusiasts have been using HGH widely since at least the 1990s because it increases lean muscle mass and decreases fat. However, for years studies failed to show that those gains enhanced athletic performance. Then in 2010, researchers at the Garvan Institute of Medical Research in Sydney, Australia, showed in a double-blind test that while HGH didn't improve strength, power or endurance, it did measurably improve sprinting speed. And subjects who received testosterone shots plus HGH improved even more.

Though that remains the only published study to show unambiguous performance enhancement, there appears to be little doubt in the sports science community that HGH helps. There's also little doubt that it's used widely at the highest level of sports, usually in conjunction with steroids.

I contacted several researchers who have published studies of HGH in sports, and all answered in emails that it's a PED.

"In a nutshell, the answer is that the cheats are right," said Peter Sonksen, an emeritus professor of endocrinology at King's College in London and a leading HGH expert. "GH works with testosterone and anabolic steroids to build muscle and tendon size and strength — it allows people to get much more muscular than the gym alone, and I have little doubt that it is a powerful drug of abuse in sport. It's at least as anabolic as testosterone."

Said Richard Holt, a professor of endocrinology at the University of Southampton in the U.K.: "I think GH improves performance for the following reasons: It is a powerful anabolic agent — shown conclusively in studies of people with GH deficiency; when the studies are done properly, GH shows performance benefit; and athletes are in a good position to determine its effects through trial of experiments."

And said Vita Birzniece, who was one of the co-authors of the aforementioned study by the Garvan Institute: "Yes, GH has an effect on performance, but it may be mostly related to anaerobic exercise capacity, which is important for short-term explosive power and sprints. And this effect of GH is enhanced by androgenic anabolic steroids such as testosterone. GH also may benefit recovery after injury as it stimulates collagen production, so tendons may heal faster."

But whether the NFL's HGH test will catch or dissuade users is another matter. There are two kinds of HGH tests, and both require blood samples. One, called an isoform, detects synthetic HGH and has been used by anti-doping agencies since 2004. The other is a biomarker, which tests for chemicals produced after HGH use and was first implemented on a large stage in the 2012 London Olympics.

The biggest problem with the isoform test is its small window, as short as 10 hours after using HGH, or at the longest, three days.

The biomarker test, which Senkson helped develop, has a much wider window of detection, anywhere from one to three weeks after HGH use. But it has problems, too. Without getting lost in details, defining a positive test has been problematic, and it appears the current parameters are so high that many users are going undetected.

The Olympics use the biomarkers test. Major League Baseball uses the isoform because no North American labs accredited by the World Anti-Doping Agency provide the biomarker. The NFL will follow MLB for now, though a league source said it will switch to the biomarkers "in due time."

Either way, HGH tests haven't caught many users, even though the general belief is that HGH is widely used at the highest levels of sport.

So far, baseball's testing at the minor-league level has yielded one positive result (Class AAA player Mike Jacobs in 2011). Offseason testing in the major leagues began in 2011, and random in-season testing was added last year, but no one has tested positive. The three suspensions in MLB that included HGH violations — including Alex Rodriguez's — were for possession, not positive tests.

And the 2012 Olympics, the first to use the biomarkers test, yielded no positives.

So look at the NFL's new HGH testing as a start. If nobody tests positive, it doesn't mean HGH use isn't high in the NFL. It only means the testing hasn't caught up.

— pdougher@pressgazettemedia.com and follow him on Twitter @PeteDougherty

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