Specialists in hormone replacement therapy (HRT) warned women in Britain yesterday not to overreact to findings by American researchers indicating that the risks of the treatment might outweigh the benefits.

Specialists in hormone replacement therapy (HRT) warned women in Britain yesterday not to overreact to findings by American researchers indicating that the risks of the treatment might outweigh the benefits.

The US trial, which has been stopped prematurely, involved more than 16,600 healthy, postmenopausal women who were taking the treatment as part of a controlled clinical study. They were not having HRT for specific medical conditions, such as severe postmenopausal disorders.

Although the relative risks appeared profound, with a 26 per cent increase in invasive breast cancer and a 29 per cent increase in heart disease, the absolute risks were what patients needed to consider, said Professor David Purdie of the Centre for Metabolic Diseases at Hull University.

The absolute risks for 10,000 women taking the American form of HRT for a year translated into an extra eight invasive breast cancers, seven more cases of heart disease and eight more strokes. These were still relatively small increases in risk, Professor Purdie said.

"Yet the benefits of taking HRT for some women are very clear. It deals with postmenopausal symptoms, reduces the risk of osteoporosis, and probably reduces the risk of colorectal cancer and even Alzheimer's disease," Professor Purdie said. "There should be no reason why women here should stop taking HRT. If women are concerned they should review the evidence with their doctors."

The Medicines Control Agency, which licenses treatments in Britain, said 6 million HRT prescriptions were issued in England last year and that the increased risk of breast cancer with combined HRT had been known for some time. "UK product information for HRT already contains extensive warnings about the risk of breast cancer," the agency said.

"When the data from the Women's Health Initiative study becomes available the MCA will rapidly assess it, seek the independent scientific advice of the Committee on Safety of Medicines and take further action as necessary."

The American study, part of the Women's Health Initiative, is the first to provide definitive data on HRT treatment for healthy, postmenopausal women with an intact womb. "This trial did not address the short-term risks and benefits of hormones given for the treatment of menopausal symptoms," said the researchers, led by Professor Jacques Rossouw of the US National Heart, Lung and Blood Institute near Washington DC.

Another member of the research team, Dr David Ontjes from the University of North Carolina, said: "This is very valuable information that applies to a large spectrum of women in the United States, and we believe it will influence physicians' practice in this area. For individual women, however, there are often considerations that might influence their decision whether to take oestrogen differently. Sometimes it's a difficult decision to make.

"We still need to learn about the long-term benefits and risk of taking oestrogen alone, a very important question for millions of women who have had a hysterectomy."

More than 2.5 million women in Britain, or one third of those aged between 50 and 64, take HRT. It is mainly taken orally as tablets, but some women have implants in the abdomen, which last for three months, and a few take it vaginally using pessaries. Women have been treated with hormones since before the the Second World War. But HRT, which was pioneered in America, only came into common use in the past two decades.

It became more fashionable in the early 1990s after reports that HRT increased longevity and protected women against heart disease. But studies at the time could have been skewed by including women who were at low risk of coronary disease because they were well-off.

More recently, research has suggested that HRT actually increases the risk of heart disease, although the American study is the first to provide definitive proof.

Today doctors are most likely to prescribe HRT because of its substantial benefits in protecting against osteoporosis, especially in women who have an early menopause or have a history of the bone disease or in women who are unusually thin.

Other benefits of the therapy include reversing vaginal dryness to help improve the sex lives of menopausal women, improving problems of urinary incontinence and reducing the effect of mood swings.

Some women say the hormones make them look younger and improve their hair and complexion. But the therapy is very rarely prescribed for cosmetic reasons.

Professor Valerie Beral, from Oxford University, is conducting a major British study, involving 1 million women, which is looking at the health risks of HRT, including the link with breast cancer.

The results of the Million Women Study will not be known for another couple of years. But research by Professor Beral in 1997 showed that HRT users in the United States had an increased risk of breast cancer.

Last night Professor Beral said the American results were "very important" particularly because they showed, for the first time, that HRT increased the risk of heart disease, strokes and blood clots.

"We have all been waiting to see the results of the study, which has been very well conducted. The excess of breast cancer is not surprising, we found that in a study a few years ago. What is surprising is the excess of heart disease and strokes. There have been hints that this might be so, but this is the first definitive evidence of that in healthy women. Some commentators are saying the types of hormones used in the States are not quite the same as over here. So the Million Women Study will be important."

The therapy replaces falling levels of the female hormone, oestrogen, in women who are going through, or who have gone through the menopause. Some women start taking HRT in their late 40s, but it is mostly taken by those between 50 and 65.

Manufacturers in the UK insisted last night that their products used different compounds to those in America and produced different responses. The results, they said, could not be applied to any form of HRT other than the one investigated in the trial.

Case Study: 'It has not been the perfect solution for me'

By Arifa Akbar

Eileen Larkin endured seven years of discomfort after experiencing an early menopause at the age of 43.

The personal assistant's most distressing symptoms included a searing hot pain running from her head to her feet, flushes and night sweats.

Miss Larkin, who lives on the Quayside in Newcastle upon Tyne, submitted to hormone replacement therapy three months ago after spending years trying to alleviate the pain using natural and alternative remedies.

While the upsetting symptoms have abated since she began HRT, she was shocked by some initial bleeding.

Miss Larkin, who has never had children, still experiences some discomfort.

She has been wondering whether she should continue taking HRT because of the complications and intends to discuss the long-term effects of the therapy with her doctor at an appointment this month.

Yesterday she expressed some concern at the findings of the American study on the long-term risks of HRT but felt that the treatment required further investigation.

"I was loath to take HRT straight away," she said. "Unfortunately, the herbal way did not help me so I began talking a substitute HRT pill which was perfect for me but was not a combination of progestin and oestrogen as HRT is."

Earlier this year she was advised to take HRT after an operation to deal with some cell abnormalities in her womb. "[The doctor] did not say it was cancer but he said that a combination HRT pill would be better for my health. While it has not been the perfect solution for me, I have friends who have been on it for 10 years and could never imagine life without it."

Miss Larkin was told by her gynaecologist that there were no significant risks of long-term side effects when she began HRTbut now wonders if she made the right decision."I was told there was quite a low percentage of women who had suffered harmful, long-term side effects or breast cancer and that is why I felt reassured," she said.