Both Major League Baseball and the NFL have now warned players about products labeled as containing velvet deer antler. But that may be all the leagues can do. That's because the banned hormone the antler products are said to include are difficult to flag -- even with blood testing.

The growth hormone associated with velvet deer antler, Insulin-like Growth Factor-1 (IGF-1), is banned by the World Anti-Doping Agency and all major sports leagues. But the national lab that tests supplements for the MLB and the NFL, NSF International, does not have a test for it.

"IGF-1 is present in all mammals, but it would be different in each species," says NSF International research scientist John Travis. "IGF-1 in a dog would be different than a cow than a human. So if the deer antler IGF-1 -- if even present -- is too different from human IGF-1, it would not be detected by the current test, leading to a false negative result."

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In other words, even if an athlete takes heavy doses of IGF-1 from velvet deer antler, a test may not always show it.

"We don't know how it's metabolizing," says Ed Wyszumiala, general manager of NSF International's dietary supplement certification program. "There's not enough scientific data."

Wyszumiala points to a 2008 report in the scientific journal Rapid Communications in Mass Spectrometry, which concludes in part: "Regarding the IGF-1 analogues as a possible threat in sports and doping control analysis, there is a lack of information because pharmacological data in humans are not currently available."

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Velvet deer antler has been used for centuries for healing purposes, mainly in Asian cultures. But only over the past few years has it made its way into mainstream American sports. In January, ThePostGame reported that new Raiders head coach Hue Jackson was told by the NFL that he could no longer endorse a supplement company that sold The Ultimate Spray, which is alleged to contain velvet deer antler. Weeks later, the NFL sent warning letters to dozens of players who had given testimonials to the company behind the spray, Sports With Alternatives To Steroids (SWATS).

Now MLB has warned its players not to use any other supplements containing deer velvet antler. But this issue may confront other leagues as well. ThePostGame has learned that several athletes across professional sports have used The Ultimate Spray, sold by S.W.A.T.S., even though it is said to contain IGF-1.

Bengals safety Roy Williams, Saints fullback Heath Evans, pro golfer Mark Calcavecchia and motocross rider Mike Metzger have all told ThePostGame they have used The Ultimate Spray. SWATS founder Mitch Ross provided several text messages from a phone number belonging to All-Pro Baltimore Ravens linebacker Ray Lewis acknowledging receipt of shipments of the spray and asking for more.

NFL spokesman Greg Aiello told ThePostGame last month he hopes the league can begin testing for IGF-1 and HGH under the new collective bargaining agreement. He added that the league can suspend a player without a positive drug test "if we have substantial evidence."

"Without the blood test, there would be no conclusive evidence," Aiello said. "But we'd like to test for it. If we could establish a player was using IGF-1 through whatever means, that player would be subject to suspension. Same with growth hormone."

Asked if the NFL would test The Ultimate Spray to determine whether it contains IGF-1, Aiello said, "We're not going to discuss what plans we may or may not have."

An email from NFL spokesman Dan Masonson received Monday said, "Our Independent Administrator regularly reviews information on substances and products and issues health alerts and other warnings when appropriate, but we will not have a comment on any particular products. Our testing plan concerns growth hormones."

An email to the PGA Tour Sunday about velvet deer antler was not immediately returned.

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In its letter to players last week, MLB voiced concern about another possible issue with The Ultimate Spray, adding it to its list of "potentially contaminated nutritional supplements." The League says it is acting on reports from drug-testers that the spray could produce positive tests for methyl-testosterone -- a banned testosterone byproduct.

This reaction comes only weeks after the $5.4 million ruling for St. Louis Rams linebacker David Vobora in his lawsuit against Anti-Steroid Program LLC, another of Ross' companies. The suit alleged that the cause of Vobora's failed drug test in 2009 was his use of The Ultimate Spray. Vobora sent the bottle of spray he claims to have used to a lab and it was found to contain methyl-testosterone.

However, Ross says he sent a bottle to NMS Labs in Pennsylvania and provided those results to ThePostGame. They came back negative for methyl-testosterone. ThePostGame sent a sample of The Ultimate Spray to respected testing lab Anti-Doping Research and those results also came back negative for methyl-testosterone. (The lab did not have a ready protocol for testing IGF-1.)

None of the athletes who have admitted using The Ultimate Spray to ThePostGame has tested positive for either IGF-1 or methyl-testosterone.

But despite the fear of a contaminant, the real threat to MLB and NFL drug policy is probably not methyl-testosterone, but IGF-1. And even blood testing, should it be approved, may not create a surefire screen for a hormone found in humans, deer, several other animal species, and even some forms of milk.

For now, the lead testing lab for both leagues, NSF International, has not heard from either league on velvet deer antler.

"I would presume one of the first labs they contact," says Wyszumiala, "would be us."

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