How Female Reproduction System Works - Getting the Great Egg Race Started

Getting the follicle-to-egg marathon running is a bit like a relay race in and of itself.

Until the primordial follicles become primary and then secondary follicles, the race primarily takes place inside the ovary on its own. But when it comes time for a group of secondary follicles to sprint to becoming the ovulated egg, hormones from outside the ovary play a more important role.

The hypothalamus gland, which is located in the brain, starts the relay race off by releasing gonadotropin-releasing hormone, or GnRH. This happens on the first day of your period.

This hormone signals the pituitary gland to generate two more hormones, follicle-stimulating hormone, or FSH, and luteinizing hormone, or LH. 

While the pituitary gland is producing both FSH and LH, it stores most of the LH for later. During the first few days of your menstrual cycle, it's the FSH that gets released the most.

This is the beginning of what is known as the follicular phase of the menstrual cycle.