Sex hormones are steroid hormones produced by the testes or ovaries that control reproductive functions and sexual development. The major sex hormones are testosterone and estrogen. Testosterone, produced by the testes, promotes male secondary sex characteristics and sperm production. Estrogen and progesterone, produced by the ovaries, bring about changes during female puberty like breast growth and prepare the uterus for pregnancy. Hormones act through the bloodstream to have effects throughout the body.