TOKYO -- When Gary Wittert began looking for tubby male baby boomers for a clinical trial last month, he got 800 volunteers in one day. The draw: free testosterone injections.Wittert, a professor of medicine at the University of Adelaide in Australia, and his colleagues suspect that the sex hormone, known to increase libido and musculature, could also help prevent a form of diabetes that tends to strike later in life and afflicts more than 330 million people worldwide.The steroid, which cyclist Lance Armstrong admitted to using in winning seven Tour de France titles, could go from being popular among men "looking to spice up their sex lives" to becoming a mainstream therapy if the trial, the largest test of testosterone's potential to fight diabetes, shows positive results, said Stuart Roberts, a healthcare analyst with Bell Potter Securities in Sydney."The Wittert study will be the real kicker here," Roberts said. "This is what gets you away from the 'snigger factor' with testosterone. And because testosterone is cheap and easy to make, it won't be an impost to the healthcare system."The study was discussed at the 10th International Congress of Andrology, which ran through Tuesday in Melbourne.Testosterone is already in demand.Revenue from prescription sales in the United States have grown 10 times over to $2.2 billion since 2001. Newer topical gel formulations are spurring 20-percent-a-year growth in the market, which will reach $5 billion by 2017.In Australia, where testosterone prescriptions are also climbing, demand is spurred by what David Handelsman, a professor of medicine at the University of Sydney, describes as an "anti-aging racket."Men "think testosterone is the essence of manhood and it will prolong their youthful vigor forever," Handelsman said. "They're persuaded because sex sells and anything to do with sex and reproduction is easy to market."