Normal menopause is a gradual process that starts between the ages of 45 and 55. It is defined as occurring in women who have at least one ovary, and takes 5 to 10 years, though it can take up to 13 years. Early menopause, on the other hand, can start in the 30's or early 40's, in women who have at least one ovary.

Premature menopause has the advantage that the whole process is usually quicker than regular menopause. 1% of women will have finished their mid life transition by the age of 40. On the whole, 1 to 3 years is shaved off.

There are a number of things that can lead to premature menopause. Sometimes these things are a result of lifestyle choices, that include:

• poor nutrition
• heavy smoking
• heavy drinking
• chronic stress to the body - this can include excessive athletic training

However, sometimes factors outside of a woman's control lead to early menopause. For example, autoimmune disorders can affect menopause as well. Mumps and other serious viral infections can damage a woman's eggs. Given that menopause is associated with fewer primary follicles being able to develop and ovulate, it is easy to see why a woman with fewer follicles, or damaged eggs unable to develop into an ovulatory egg, is prone to an earlier menopause.

If a woman has undergone radiation therapy or chemotherapy, large numbers of eggs can be destroyed. With fewer eggs left, menopause will be earlier than in healthy women.

Some women are just born with fewer eggs. They will also experience premature menopause. When a woman's mother underwent menopause is a good guide to her own genetic predisposition.

Women who have had their ovaries removed before they experience a natural menopause will undergo what is called 'artificial menopause'. This is a very abrupt form of menopause, and hormone replacement therapy is usually recommended because the body has not had a chance to get used to the hormonal changes.

Women who have a hysterectomy, even with the preservation of their ovaries, may find themselves having menopausal symptoms. Any surgery to the pelvic area can disrupt blood flow and cause ovarian failure.

Ovarian failure does not necessarily mean that the ovaries have run out of eggs. There may be eggs present, but a woman's body does not respond to the hormonal signals they create.

Another ovarian disorder, called 'diminished ovarian reserve', is often a preamble of premature ovarian failure if it occurs in woman under the age of 40. In it, a woman may still have reasonably regular periods, but she begins to experience the symptoms of menopause.

References: Dr Christiane Northrup, The Wisdom of Menopause