The first 12 days
For the first 12 days of the menstrual cycle, estrogen has a negative effect on the production of gonadotropins.
Following these 12 days the negative effect changes to a positive effect on the production of gonadotropic hormones.
This results in a small increase of follicle stimulating hormone (FSH), but a large increase of luteinizing hormone (LH).
This sudden increase of LH causes the mature follicle to release the egg. Following release of the ovum, the ruptured ovarian follicle develops into the corpus luteum.
End of the cycle
The corpus luteum, in turn, secretes estrogen and progesterone. These ovarian hormones are important for the maintenance of the endometrial lining of the uterus where the blastocyst implants itself.
Continued high levels of estrogen and progesterone produce a negative feedback on the secretion of gonadotropins by the anterior pituitary gland.