Hormones are chemical messengers produced by specific organs in the body that travel in the blood to target tissues and influence behavior and physiology. The major hormone of interest to us is progesterone, a steroid hormone produced by the ovary and placenta in females. The body is constantly churning out new hormones, while destroying the old ones in the liver or eliminating them in urine and feces. Our interest lies in the reproductive endocrinology, or hormones related to reproduction, of