What does natural testosterone do for a man’s health? Testosterone is the fundamental life force that makes a man a man, and the driving energy that keeps guys fit, strong, and virile. Many men suffer from various degrees and symptoms of low testosterone. Signs of low testosterone include: Lack of energy, moodiness and irritability, depression, muscle atrophy, loss of libido, etc. Click through to learn about the options to boost testosterone in men! Please re-pin to help us educate others.