Progestogens, also sometimes written progestins, progestagens or gestagens,[1] are a class of natural or synthetic steroid hormones that bind to and activate the progesterone receptors (PR).

The progestogens are named for their function in maintaining pregnancy (i.e., progestational), although they are also present at other phases of the estrous and menstrual cycles.

In addition, they are one of the five major classes of steroid hormones, the others being the androgens, estrogens, glucocorticoids, and mineralocorticoids, as well as the neurosteroids.

The terms progesterone, progestogen, and progestin are mistakenly used interchangeably both in the scientific literature and in clinical settings.

The major tissues affected by progestogens include the uterus, vagina, cervix, breasts, testes, and brain.

The main biological role of progestogens in the body is in the female reproductive system, and the male reproductive system,[19] with involvement in regulation of the menstrual cycle, maintenance of pregnancy, and preparation of the mammary glands for lactation and breastfeeding following parturition in women; in men progesterone affects spermiogenesis, sperm capacitation, and testosterone synthesis.

The endogenous progestogens are naturally occurring pregnane steroids with ketone and/or hydroxyl groups at the C3 and C20 positions.