The primary male sex hormone produced by the male gonad or testes is called testosterone.
The specialized cells called Leydig cells located between the seminiferous tubules in the testes are responsible for the production of testosterone.
Function:
Testosterone is involved in the development of the male secondary sex characteristics such as facial hair, pubic hair, increased muscular build, deep voice, etc.
It is involved in increasing the protein synthesis in muscles thereby increasing the muscle mass in males.