What role do hormones play?

Ovarian follicle development is triggered by FSH from the pituitary gland. The follicles produce oestrogen. This causes the pituitary gland to release a burst of LH that cuts FH production.

The LH triggers the release of the egg from the most mature follicle and the corpus luteum. This forms from the follicle after the egg has been released, then produces progesterone.