<P> The follicular phase is the phase of the estrous cycle, (or, in humans and great apes, the menstrual cycle) during which follicles in the ovary mature . It ends with ovulation . The main hormone controlling this stage is estradiol . </P> <P> Follicle - stimulating hormone (FSH) is secreted by the anterior pituitary gland . FSH secretion begins to rise in the last few days of the previous menstrual cycle, and is highest and most important during the first week of the follicular phase . The rise in FSH levels recruits five to seven tertiary - stage ovarian follicles (this stage follicle is also known as a Graafian follicle or antral follicle) for entry into the menstrual cycle . These follicles, that have been growing for the better part of a year in a process known as folliculogenesis, compete with each other for dominance . </P>

When does the follicular phase of the ovarian cycle occur