It's supposed to be a precursor to testosterone, but when you take it, you never know how much will really convert. There was a lot of hype about it when it first came out, then when people realized it didn't help you unless you were deficient, interest dropped off. I have no idea what the reasoning is behind making it illegal in Australia except for the fact that it is chemically related to testosterone. Lawmakers often go off the deep end trying to "protect."