During the proliferative stage of the menstrual cycle, a cohort of primordial follicles begins to develop in the ovary due to the increase in FSH hormone by the pituitary gland. This follicular growth induces the production of estradiol by the ovary, which acts on the pituitary gland with negative feedback, i.e. it slows down the production of FSH.
The consequence of decreased FSH is follicular recruitment: only one of the follicles will be able to respond to the low FSH level to continue its development and become a preovulatory follicle. The rest of the follicles will not reach maturity and will degenerate.