<P> 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 asthmatics should take great care when handling this hormone as PGF2a is bronchoconstrictor . </P> <P> Estrogen, secreted by Granulosa Cells and primarily progesterone, secreted by the corpus luteum, inhibit the release of luteinizing hormone (LH) and Follicle Stimulating Hormone (FSH) 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). During a pregnancy, the corpus luteum remains on the ovary releasing progesterone which will maintain a state of uterine quiescence and close the cervix until the delivery of the fetus . Alternatively if no implantation of a blastocyst occurs, the corpus luteum is degraded to a corpus albicans (scar tissue) by PGF2alpha released by uterine endometrial cells . </P> <P> 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 . </P> <P> If pregnancy occurs, the placental hormone chorionic gonadotropin continues to maintain the corpus luteum, but in some species it will eventually degrade sometime during pregnancy . </P>

What is the result when the progesterone level drops from a regressing corpus luteum