Luteolysis

Luteolysis is the structural and functional degradation of the corpus luteum that occurs at the end of the luteal phase in the absence of pregnancy. It is caused by the hormones prostaglandin-F2alpha and oxytocin. Communication between the corpus luteum and the uterine endometrium is required for luteolysis. Studies with sheep have found that if the uterus is surgically removed, it can extend the life of the corpus luteum drastically.

Luteolysis in humans and other primates however is not caused by prostaglandin and removal of the uterus will not prolong the life of the corpus luteum. Oestrogen and progesterone, secreted by the corpus luteum, inhibit the release of Luteinising hormone (LH) by the adenohypophysis (anterior pituitary gland). This removes the luteotrophic support provided by the luteinising 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 in 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.

References

*Bagnell, C. 2005. "Animal Reproduction". Rutgers University Department of Animal Sciences.