Progesterone is one of two main hormones produced by the ovaries.
More specifically, it is produced by the corpus luteum just after ovulation. Progesterone is responsible for preparing and maintaining the lining of the uterus in preparation for the fertilized egg. Progesterone secreted from the ovary is necessary for the survival of the ovum and the resulting embryo until the placenta takes over this production. The decline in progesterone each month triggers the menstrual cycle. Progesterone and estrogen are closely interrelated and their actions in the body are in a delicate balance.