Testosterone is one of the hormones needed for sexual development and is present in everyone. Testosterone is mostly made in the testicles, which are part of the male reproductive system. But small amounts are also made by the ovaries, which are part of the female reproductive system, and the adrenal gland. Testosterone is considered an androgen, which is a male sex hormone.

Testosterone helps strengthen bones and muscles. During male puberty, testosterone signals the body to lower the voice, grow facial hair, and develop male sexual characteristics. Testosterone is also one of the hormones needed by the testicles to make sperm.

Testosterone is also a medicine made in a lab. It may be prescribed by a doctor to treat medical conditions, such as when a person's natural level of testosterone is too low. This type of testosterone is also used in gender-affirming care.