The menopause occurs in all women. It can occur when the ovaries spontaneously fail to produce the hormones estrogen and progesterone, 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. Ovaries naturally fail to produce estrogen and progesterone when they have few remaining egg cells. At that stage, the ovaries become less able to respond to the pituitary hormones: follicle stimulating hormone (FSH) and luteinising hormone (LH) and less estrogen is produced. Levels of FSH and LH subsequently rise and a measurement of FSH is sometimes used to diagnose menopause. The resulting low, and changing levels of ovarian hormones, particularly estrogen, are thought to be the cause of menopausal symptoms in many women.

The term climacteric refers to the time in which the hormone levels are changing, up to the periods stopping; reducing and fluctuating hormone levels can cause early menopausal symptoms while still stimulating the endometrium (lining of the womb) to produce cyclical bleeding (menstruation).

Menopause means the last menstrual period. Periods stop because the low levels of estrogen and progesterone do not stimulate the lining of the womb (endometrium) in the normal cycle. Hormone levels can fluctuate for several years before eventually becoming so low that the endometrium stays thin and does not bleed.

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 with intact ovaries, or immediately following surgery if the ovaries have been removed.

Menopause - when?

The average age of the natural menopause is 51 years, but can occur much earlier or later. Menopause occurring before the age of 45 is called early menopause and before the age of 40 is premature menopause.
(The Daisynetwork registered charity and support group is for women suffering from premature menopause www.daisynetwork.org.uk)
Visit the International Premature Ovarian Failure Association at www.pofsupport.org

For further reading, we recommend 'Premature Menopause Book: When the "Change of Life" Comes Too Early by Kathryn Petras ' - on the recommended reading page.

Premature or early menopause may follow surgery such as hysterectomy when the ovaries may be removed along with the womb, or may occur early even if the ovaries are left in place at the time of hysterectomy. Other causes of early or premature menopause include chromosomal disorders such as Turner's syndrome (www.tss.org.uk) and Down's syndrome, autoimmune disorder (when antibodies which work against the ovaries are produced), and chemotherapy or radiotherapy. Some drugs may stop the ovaries functioning early but usually ovarian function resumes when the drug is stopped. Often there is no obvious cause of premature or early menopause.
Women who have chromosomal disorders often do not have periods at all since their hormone levels have always been low. They may not experience the usual menopausal symptoms since they do not have changing hormone levels. Despite the lack of symptoms, discussion about hormonal treatment is vitally important, as it is for all women with premature menopause because of the increased risk of osteoporosis; estrogen, either when produced naturally or when taken as medication, is very important in maintaining bone density and preventing bone loss. The lack of estrogen at a younger age than normal therefore increases the risk of bone loss and osteoporosis. Generally, women having an early or premature menopause are advised to take HRT until approximately the average age of the menopause, for both symptom control and bone protective effect. Late menopause may also occur but by the age of 54, 80% of women will have stopped having periods.

Related Sources: Management of the Menopause; the handbook of the British Menopause Society.