Hint: Progestational hormones are a class of sex hormones associated with certain changes in the uterus and vagina during the menstrual cycle. They are necessary for the development of mammary tissue and for the maintenance of pregnancy.
Complete answer: Progesterone is the major and most important progestogen in the body. The progestogens are named for their function in maintaining a pregnancy (i.e., progestational), although they are also present at other phases of the estrous and menstrual cycles. Progesterone (P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It is also a crucial metabolic intermediate in the production of other endogenous steroids, including the sex hormones and the corticosteroids, and plays an important role in brain function as a neurosteroid. Progesterone is a hormone released by the corpus luteum in the ovary. It stimulates the formation of the milk glands. These hormones are believed to be responsible for the cyclical changes that many women feel in their breasts just before menstruation. These include swelling, pain, and soreness. During implantation and gestation, progesterone appears to decrease the maternal immune response to allow for the acceptance of the pregnancy.
Note: Progesterone is also used as a medication, such as in menopausal hormone therapy. Progesterone, through its neurosteroid active metabolites such as 5α-dihydroprogesterone and allopregnanolone, acts indirectly as a positive allosteric modulator of the GABA receptor.