During an unmedicated cycle, progesterone is produced by the corpus luteum, a cyst-like structure formed after the oocyte is released from its ovarian follicle. Progesterone vascularizes the uterine lining, increasing the blood supply in preparation for potential implantation of a fertilized egg. In the absence of pregnancy, the corpus luteum's progesterone output will normally begin to decrease after about 12 days. In response, the vascularized lining is shed in the form of a period.
Because of these effects, the primary uses of progesterone in infertility treatment are (1) triggering of menstruation and (2) luteal phase supplementation. |
