During the menstrual cycle, the pituitary gland releases FSH (follicle stimulating hormone) which causes the egg to mature in the ovaries and stimulate the ovaries to produce oestrogen. The pituitary gland also releases LH (luteinising hormone) which stimulates the release of mature eggs from the ovaries during ovulation. The ovaries release oestrogen, causing the lining of the uterus wall to thicken, inhibits the release of FSH and stimulates the release of LH. The ovaries also release progesterone, maintaining the thick uterus lining and inhibits the release of FSH and LH