Testosterone is the primary sex masculine hormone.
It plays several important roles, such as:
- The development of the penis and testes;
- The deepening of the voice during puberty;
- The appearance of facial and pubic hair starting at puberty;
- Muscle size and strength;
- Bone growth and strength;
- Sex drive (libido);
- Sperm production.
Adolescent boys with too little testosterone may not experience normal masculinization. For example, genitals may not enlarge, and the voice may not deepen normally.
Signals sent from the brain to the pituitary gland control the production of testosterone in men. The pituitary gland then relays signals to the testes to produce testosterone.
- A feedback loop closely regulates the amount of testosterone in the blood. When testosterone levels rise too high, the brain sends signals to the pituitary to reduce production.
Testosterone is also essential in females. These hormones are thought to have important effects on ovarian function, bone strength, and sexual behavior.