Testosterone has different roles in different life stages. During fetal development, it triggers the development of male internal and external reproductive organs. In puberty, it is responsible for the changes seen in males, such as height increase, body and pubic hair growth, and enlargement of the penis, testes, and prostate gland. In adulthood, testosterone is essential for sperm production, signals the body to make red blood cells, ensures bone and muscle strength, and enhances libido and well-being.