The testes produce both sperm and the androgenic hormone testosterone, which is a vital hormone for male development, driving the changes that take place during puberty. However, testosterone isn't the only hormone that the testicles produce. The testes also synthesize anti-Müllerian hormone, insulin-like factor 3 and estradiol.
In addition to its importance in puberty, testosterone also plays a vital role in the earliest stages of male development within the fetus. During puberty, increasing levels of testosterone trigger changes, such as an increase in facial hair growth, deepening of the voice and the male growth spurt. Throughout a man's life, testosterone acts to drive sperm production.
Testosterone is released from the testes by Leydig cells that lie between structures called seminiferous tubules.