Androgens
This is a group of sex hormones that help create male sex characteristics and masculine traits. Androgens help with normal development of the penis and testicles in male fetuses. At puberty, androgen levels go up and cause secondary male sex characteristics such as facial hair, pubic and underarm hair, growth of the penis, sperm formation, muscle development and growth in height. Girls make androgens, too, but in much smaller amounts than boys.