Progesterone This is the hormone secreted after ovulation by the corpus luteum. It is a steroid (similar to a cholesterol), enters receptive cells to stimulate their growth, and acts as an anabolic agent. Estrogen should be viewed as the primary coat underneath all the cycles during a woman's reproductive years, with progesterone, its antagonist, surging for ten or twelve days in ovulatory months. Most of the actions of progesterone cannot occur without estrogen having previously induced the growth of progesterone-receptive binding sites.
