Why would I have progesterone in my ovary?

You would not typically find significant amounts of progesterone in your ovary. Progesterone is primarily produced by the corpus luteum, a temporary structure that forms in the ovary after ovulation. It is responsible for maintaining the uterine lining and preparing it for implantation of a fertilized egg. If implantation does not occur, the corpus luteum regresses, and progesterone levels decrease, leading to the onset of menstruation.