TRT is permitted provided your levels are within the acceptable range when tested for events. Guys like Henderson, Couture and even Marquardt 'legally' use testosterone. Keep in mind, the UFC didn't have an issue with Marquardt's 'therapy'. Marquardt's problem is that once he informed the UFC and NSAC that he was undergoing TRT they wanted to monitor his levels prior to his fight. And the dude didn't get them down to acceptable levels.