From your menarche, the first period, to your menopause (Greek: men- month; pausis cessation) the endometrium (lining of the womb) changes its structure cyclically under the influence of the sex steroids hormones, oestrogen and progesterone with menstruation marking just one of these cyclical changes. The menstrual cycle is interrupted by pregnancy when specific endometrial changes occur (decidualisation). The menstrual cycle is controlled by hypothalamic and pituitary hormones (the hypothalamus and pituitary gland are situated at the base of the brain) and by ovarian hormones. (Figure 2.6)
