White flowers in a vase with water (Menopause Clinic Liverpool)All women will experience the menopause. Menopause can occur either naturally when the ovaries fail to produce hormones oestrogen and progesterone-periods stop because the low levels of estrogen and progesterone do not stimulate the endometrium (lining of the womb). Hormone levels can fluctuate for many years before eventually becoming so low that the endometrium stays thin and does not bleed. Menopause can also occur when the ovaries fail due to specific treatment such as chemotherapy or radiotherapy, or when the ovaries are removed, often at the time of a hysterectomy. Occasionally ovaries fail for no known reason. 

The resulting low and changing levels of hormones, particularly oestrogen, are understood to be the cause of menopausal symptoms. Menopause means the last menstrual period.

Perimenopause is the stage from the beginning of menopausal symptoms to the postmenopause.

Postmenopause is the time following the last period and is usually defined as more than 12 months with no periods in someone who has their ovaries, or immediately following surgery if the ovaries are removed.

The average age of the menopause is 51years but can occur much earlier or later. Menopause occurring before the age of 45 is called an early menopause and before the age of 40 is a premature menopause/ premature ovarian insufficiency.