Progesterone is a steroid hormone that plays a crucial role in regulating female reproductive function. In the menstrual cycle, progesterone is produced by the ovary following ovulation and helps prepare the lining of the uterus for possible implantation by a fertilized egg. If pregnancy occurs, progesterone production is taken over by the placenta to support pregnancy and prevent miscarriage. If pregnancy does not occur, progesterone levels drop and this triggers menstruation.

Progesterone is also used in hormone replacement therapy for menopausal women and to support pregnancy in women undergoing assisted reproductive technologies, such as in vitro fertilization. Low levels of progesterone can lead to infertility, irregular menstrual cycles, and miscarriage.