Testosterone is the main sex hormone (androgen) in men. It is responsible for male physical characteristics. Although it is considered to be a “male” sex hormone, it is present in the blood of both men and women. This test measures the level of testosterone in the blood.
Testosterone is mainly produced by special endocrine tissue (the Leydig cells) in the male testicles. It is also produced by the adrenal glands in both males and females and, in small amounts, by the ovaries in females.
In males, testosterone stimulates development of secondary sex characteristics, including enlargement of the penis, growth of body hair, muscle development, and a deepening voice. It is present in large amounts in males during puberty and in adult males to regulate the sex drive and maintain muscle mass. In women, testosterone is converted to estradiol, the main sex hormone in females.