Drugs used to regulate and control the reproductive system are often naturally occurring hormones or chemical modifications of hormones. These are often used to induce or suppress estrus, the time during the reproductive cycle in animals when the female displays interest in mating, often called “heat.” Some are also used to stimulate testicular function or sperm production. Some of the more commonly used hormones include gonadotropin-releasing hormone and related drugs, follicle-stimulating hormone, human chorionic gonadotropin, equine chorionic gonadotropin, estradiol compounds, progesterone and synthetic progestins, testosterone, and prostaglandins. Another hormone, oxytocin, is used to promote milk production and letdown and to cause contraction of the uterus to either induce labor or to enhance contraction of the uterus after the birth.
