And the Lutonizing hormone stimulates the corpus luteum to produce not only estrogen but another type of hormone known as progesterone. Now, estrogen initiates the thickening of the endometrium but progesterone actually maintains that thickening process. What it also does is it basically inhibits the contraction of the muscle found inside the uterus and it also inhibits the production of secondary follicles. Now notice what it does to the hypothalamus and to the interior pituitary gland, the progesterone as well as the estrogen that is produced by the corpus luteum. Now, instead of creating a positive feedback loop as it did before Ovulation post Ovulation these two hormones create a negative feedback loop. So they basically cause the hypothalamus to release less GnRH.