What hormone is primarily responsible for preparing the endometrium for fertilization during the luteal phase?

During the luteal phase of the menstrual cycle, progesterone plays a critical role in preparing the endometrium for potential fertilization and implantation of a fertilized egg. After ovulation, the corpus luteum forms and secretes progesterone. This hormone causes the endometrial lining to become thicker and more vascular, creating a supportive environment for a fertilized embryo.

Progesterone also helps to maintain the uterine lining and suppresses any further ovulation during this phase, ensuring that the uterus is primed for a possible pregnancy. If fertilization does not occur, the levels of progesterone will eventually decline, leading to the breakdown of the endometrium and the onset of menstruation.

Other hormones listed, such as estrogen, also contribute to the menstrual cycle but primarily play more significant roles in the follicular phase and the initial stages of preparing the endometrium. FSH and LH are involved in stimulating ovarian function and ovulation rather than directly preparing the endometrium for implantation. Hence, progesterone is the key hormone during the luteal phase for preparing the uterus for fertilization.