During the follicular phase of the menstrual cycle, FSH encourages the formation and development of ovarian follicles (eggs) in women. FSH starts the follicle's synthesis of oestradiol during the follicular phase, and the two hormones cooperate to promote the growth of the egg follicle. FSH encourages progesterone production during the luteal phase. Oestradiol and progesterone both assist the pituitary in regulating the quantity of FSH secreted. The ovaries stop producing at menopause, and FSH levels increase. FSH encourages men's testicles to generate mature sperm. After puberty, the FSH levels in men remain largely constant.