Menarche

At about age eight, the pituitary gland secretes hormones until the ovaries begin their own production of steroids (estrogens), the chemicals that are responsible for initiating puberty. These hormones (known as the follicle stimulating hormone [FSH] and luteinizing hormone [LH]) allow for an increase in adipose tissue (fat), and inhibit the growth hormone. They stimulate the ovary to produce estrogen and progesterone, which results in breast development and pubic hair.

At birth, the human female has approximately 750,000 primordial follicles (eggs). By puberty, 400,000 remain. At or soon after menarche, the first mature egg is released. Menstruation will recur each month until menopause when few or no follicles remain. (Guyton 1976).