After years of formulation, Twinlab is proud to introduce Tribulus Fuel Extreme, a powerful Tribulus Terrestris supplement! Tribulus Fuel Extreme is a Tribulus Terrestris supplement with 20% standardized extract of the active ingredient, Protodioscin the ingredient thought to be most responsible for raising testosterone levels naturally. Increase Testosterone Levels Naturally with Protodioscin! What is most unique about Tribulus Fuel Extreme is that is has a high dose of Protodioscin, the active ingredient in Tribulus Terrestris. Each serving of Tribulus Fuel Extreme contains a minimum of 20% Protodioscin extract. Protodioscin is the ingredient that is thought to be responsible for most of the beneficial effects of Tribulus Terrestris.* Protodioscin works by stimulating the body's production of Lutenizing Hormone (or pre-testosterone), which in turn promotes the production of Testosterone, the key male hormone responsible for helping to add lean body mass, increase metabolism and support healthy libido.*