Pregnant mare serum gonadotropin (PMSG) is a gonadotropin used to promote follicular development and ovulation in animals. PMSG exerts its regulatory effects by stimulating changes in blood hormones, gonadotropins, and cytoplasmic estradiol receptors in the anterior pituitary and hypothalamus. PMSG is commonly used in livestock to improve reproductive efficiency and can also be utilized for research on estrous cycle regulation.