• Pre-menopause:
  the time from the onset of menstrual periods (“menarche”) until the start of peri-menopause. Before menopause (pre-menopause), the ovaries release an egg each month. If you do not become pregnant, the lining of the womb breaks down leading to monthly menstruation (‘periods’). During pre-menopause, the ovaries produce three main hormones: oestrogen, progesterone and testosterone.​
   
• Peri-menopause (the menopause transition):
  the time from the onset of irregular periods or vasomotor symptoms (hot flushes and night sweats) until 12 months after the final menstrual period. During peri-menopause, menstrual periods become irregular and menopausal symptoms such as hot flushes may occur. The duration of peri-menopause varies in individual women. During this time hormone levels commonly change from the monthly patterns seen during the pre-menopause. Because many organs in the body including the uterus (womb), vagina, vulva, breast, bone, bladder, brain, and skin are sensitive to these hormones, this can cause a wide range of symptoms which may affect both physical and emotional wellbeing.
   
• Menopause: 
  the final menstrual period. Eventually, menstrual periods stop completely (menopause) and the type and level of hormones produced by the body changes.
   
• Post-menopause: 
  the time from 12 months after the final menstrual period. After menopause, the ovaries produce less oestrogen and no progesterone. Some oestrogen is still produced by other tissues, particularly in fat. Testosterone levels fall slowly from the mid 20’s onwards but can drop suddenly in women who have their ovaries removed before they have reached menopause.

Hormone production and menopause

The hormone changes that occur during peri-menopause and at menopause affect the body in different ways:

• loss of oestrogen is the main cause of menopausal symptoms
• loss of progesterone is unlikely to cause symptoms
• loss of testosterone may affect sex drive (libido) and energy levels in some women.

Menopause can cause a number of different symptoms and can increase the risk of other health conditions such as osteoporosis (thinning or weakening of the bones).