Since HGH-releasing drugs don't contain growth hormone, but instead spur the body's production of it, there's no way to identify them through the current testing method, Sonksen said.
http://www.usatoday.com/sports/2008-05- ... over_N.htm
HGH releasers come in two forms. There's an easily obtainable sports supplement taken orally that, according to some studies, has questionable value. Then, there's a pharmaceutical version that's injected daily.
No athletes are known to have used it, but it worries anti-doping experts and federal drug enforcement officials because its impact is unquestioned, the government's regulations don't cover it and testing for it is beyond researchers' present reach.