Vixea Manplus needed. Testosterone replacement therapy suppresses the pituitary gland hormones responsible for sperm production. This is like a birth control pill. But if a man is deficient in testosterone, and wants to have children, we must take a different approach. Low testosterone can affect the body, but Manplus can too much of this hormone make men too aggressive? This is Lyon, home of the French Center for Cognitive Neuroscience. Jean-Claude Dreher is director of research here. Dreher has studied the effect of testosterone on human behavior, and he found little evidence that testosterone triggers aggression in men. The effect of testosterone on human behavior is .