The key to masculinity and vitality is the human growth hormone that separates the boys from the men. It plays a vital role in the creation of muscle mass and strong bones. It contributes to deep voice and even sex drive. Low testosterone in men is known as hypogonadism. As a product of a modern world made for convenience the male body does not go through nearly as much rigorous activity. The lack of daily exercise contributes to the decrease in male testosterone. It can hit as early as the mid 20s and steadily decrease each subsequent year.