Testosterone is a hormone found in humans. For people with penis testosterone is produced by the testicles, for people with vulva testosterone is produced by the ovaries. The production of the hormones vary between people with penis and people with vulva. People with vulva produce small quantities of testosterone as they are not the primary hormones responsible for fertility. Testosterone is a primary hormone responsible for the production of sperms for people with penis they are called the sex hormone for people with penis as they are responsible for the sexual development for people with penis. Low testosterone levels in people with penis can lead to infertility.