While the manager left to find the keys to the bathroom Derek's mind began to come back from the sexual overload it experienced. But even while he was just beginning to come back his oversized balls were doing what they naturally did, produce testosterone. But being so huge they produced enough testosterone fill an army of men, but all of it was being pumped into Derek's body.
When his mind fully reinserted itself it was suddenly was met by the effects of the testosterone on his mind. He could almost feel the flood of testosterone through his body. It was like going through a third puberty! Except where puberty goes for a few years, the massive amounts of testosterone was big enough to show signs immediatly.