Progesterone
Sorry, this answer is incorrect. Progesterone is an important female hormone that plays an active role in the female menstrual cycle, pregnancy, and embryogenesis of humans and other species. Its primary function in female reproduction is to prepare the endometirum for implantation. If implantation does not occur, progesterone levels drop and menstruation occurs. During pregnancy progesterone levels increase significantly. It is a steroid hormone and derived from cholesterol.