Menopause occurs when a woman no longer ovulates and the hormones oestrogen and progesterone decline. A woman is considered menopausal when she has not had a menstrual period for 12 months, however, symptoms triggered by hormonal changes can start much earlier, in what doctors call perimenopause — the perimenopause stage lasts on average 4 years.
The average age a woman will become menopausal is 51, but it will generally begin between the ages of 45-60. Most women have symptoms for 5 to 10 years, with the average duration of menopausal symptoms being 7 years.