It passes across the cell membrane and it binds onto protein receptors inside the target cell. Now, progesterone is stimulated by the luteinizing hormone LH that is released by the anterior pituitary gland. So as our amount of LH in the blood increases, the amount of progesterone released also increases. Now progesterone is initially released by the corpus luteum. So after ovulation takes place and the ovum is released into our parrot meal cavity, the corpus luteum eventually forms and that corpus luteum begins to release our progesterone hormone. Now, once our corpus luteum actually degenerates during the process of pregnancy, our placenta, the structure that basically supplies the growing fetus with nutrients, begins to release our progesterone.