Final answer:
Estrogen, produced by the follicles, initiates the preparation of the endometrium for potential pregnancy by thickening the lining, while after ovulation, progesterone from the corpus luteum takes over to maintain the environment.
Step-by-step explanation:
The hormone that is produced by the follicle and initiates the preparation of the endometrium of the uterus for pregnancy is estrogen. During the first half of the menstrual cycle, estrogen is produced by the follicles and works to thicken the endometrial lining, preparing it for potential implantation of a fertilized egg. After ovulation, the corpus luteum begins to secrete both progesterone and estrogen, which continue to prepare the endometrium for potential pregnancy. Progesterone specifically inhibits the release of further Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH), ensuring no other eggs are developed during this time.