Menopause

It normally occurs between the mid 40s and late 50s, although it can occur much earlier, and in extreme cases even in childhood.

Once the supply of hormones has fallen away, a woman will eventually cease to have a monthly menstrual cycle.

Once the cycle has stopped for at least a year, it is highly unlikely that a woman can become pregnant.

The menopause can also be brought on early by surgical removal of the ovaries, or certain types of chemotherapy treatment for cancer.

As well as the loss of the ability to bear children, women can suffer other unpleasant symptoms as the supply of sex hormones stops.

These include hot flushes - a sudden sensation of uncomfortable heat -and vaginal dryness, which can make sex painful.

In addition women can suffer a reduced sex drive, and there is an increased risk of brittle bone disease, as hormones offer natural protection.

Hormone replacement therapy

Some women alleviate these symptoms and reduce the risks by taking hormone replacement therapy (HRT).

The main component of HRT is oestrogen, although, because if giving alone this appears to increase the risk of cancer of the lining of the womb (endometrium), and possibly breast cancer, it is normally added to progestogen to reduce this possibility.

But the drugs can still cause fluid retention, headaches, mood changes and breast tenderness.

Occasionally, testosterone is given if the woman is suffering a greatly reduced sex drive.

Premature menopause

Although the menopause normally happens in late middle-age, it can be suffered far earlier.

Even young children can become fertile and move to the menopause within a matter of a few years because of growth hormone problems.

The most common causes of premature menopause are man made - situations in which the ovaries have to be removed surgically, or in which hormone producing tissue has been destroyed by chemotherapy such as the breast cancer drug Tamoxifen.

Very often, women whose ovaries have been removed or damaged because of a cancer are also denied the benefits of HRT because of fears that the hormones could promote the growth of new cancer cells.

It is currently possible to freeze eggs in advance of chemotherapy treatment or surgery, but the chances of a successful pregnancy are low.

A technique pioneered in the UK in which frozen ovary tissue is re-implanted into a post-menopausal woman could be one solution to the misery of premature menopause, and there is potential to delay or even reverse the menopause in older women.