Luteolysis

Luteolysis is the structural and functional degradation of the corpus luteum (CL), which occurs at the end of the luteal phase of both the estrous and menstrual cycles in the absence of pregnancy. In domestic animals, luteolysis is inititated by the hormones prostaglandin F2alpha and oxytocin. In sheep, communication between the pars nervosa (posterior lobe of the pituitary gland), corpus luteum, and the uterus endometrium via the circulatory system is required for luteolysis. Studies with sheep have found that, if the uterine horn ipsalateral to the ovary possessing the CL is surgically removed, the lifespan of the corpus luteum will increase drastically.

Luteolysis in primates (including humans), however, is not caused by prostaglandin, and removal of the uterus will not prolong the life of the corpus luteum. However, primates do respond to PGF2a, and women and asthmatics should take great care when handling this hormone.

Oestrogen and primarily progesterone, secreted by the corpus luteum, inhibit the release of Luteinizing hormone (LH) by the adenohypophysis (anterior lobe of the pituitary gland) via classical negative feedback mechanisms. This removes the luteotrophic support provided by the gonadotropin Luteinizing Hormone (LH), and the corpus luteum degrades to a corpus albicans (scar tissue), which is eventually absorbed into the ovary.

Degradation of the corpus luteum will result in reduced levels of progesterone, promoting an increase in follicle-stimulating hormone (FSH) secretion by the adenohypophysis, which will trigger the development of a new follicle on the ovary.

If pregnancy occurs, the placental hormone chorionic gonadotrophin continues to maintain the corpus luteum, but in some species it will eventually degrade sometime during pregnancy.