Experts have urged women in the UK taking hormone replacement therapy not to panic after a study showed the treatment could cause serious health problems.

The government has asked the experts on its Committee for Safety of Medicines to look at HRT and report back to ministers, in the light of the study findings.

Early results from a clinical trial carried out in the US suggest long term use of one type of HRT may bring a slightly increased risk of breast cancer, heart disease and stroke.

The findings caused so much concern that US authorities ordered researchers to end the study, involving more than 16,000 women, three years early.

HRT facts

6m UK women take HRT every year More than 50 different types of HRT on sale in the UK HRT can be made from human or horse hormones

But experts in the UK say the risks of cancer or heart disease remain small and women should consult their doctors before deciding to stop taking HRT.

The combination used in the study is not available in Europe, although similar ones are. An estimated 300,000 British women take this type of HRT.

'No emergency'

The US study found women who took a combination of equine hormones oestrogen and progestin were 26% more likely to develop breast cancer.

It also found the hormones increased the risk of heart attacks by 29%, strokes by 41% and doubled the risk of blood clots.

These figures represent a slightly increased risk. For instance, among 10,000 women there would be just eight extra breast cancers, eight strokes, eight blood clots and seven coronary heart disease events per year.

While the treatment reduced hip fractures and colon cancer, US authorities ruled the risks far outweighed the benefits and ordered researchers to end their study.

Professor Beral urged women not to panic

The trial, carried out as part of the US Women's Health Initiative, involved 16,608 women between 50 and 79.

However, the researchers have moved to allay fears.

Dr Jacques Rossouw, acting director of the Women's Health Initiative, told the BBC: "It's not an urgent alert situation. There's no emergency here.

"If you use it for several years, you are not likely to gain health - you are likely to lose health."

Scientific advice

The Medicines Control Agency, which licences treatments in the UK, said it would examine the results as soon as possible.

A spokesman said: "UK product information for HRT already contains extensive warnings about the risk of breast cancer.

Charities have urged women to discuss concerns with their GP.

It's absolute nonsense to scare women off this kind of treatment

Former Tory MP Teresa Gorman

Malcolm Whitehead, director of the Amarant Trust which provides help to menopausal women, said not every type of HRT had the same effect.

"This particular combination is not available here or in Europe, but similar ones are, and if you are having long-term treatment you should go to your doctor and talk about the risks and whether you should continue," he said.

Risks low

Professor David Purdie, from the Centre for Metabolic Disease at Hull Royal Infirmary, told BBC News Online: "No British women should stop taking HRT on the basis of these results and if she is at all concerned she should discuss it with her doctor.

Professor Valerie Beral of Oxford University, who is also carrying out a study into HRT, said the results were very important.

But she added: "There is no need to panic and I think really people were very surprised that this study published its results early. We really need to look at the results."

Professor Klim McPherson of the University of Bristol, said the findings "will worry women".

But he added: "You can take HRT for short periods of time maybe two or three years without having really any effect on the risks of these diseases."

Industry view

A spokesman for the UK industry-supported organisation HRT Aware said: "The specific dose investigated is not available in the UK, but if women need further information about the type of HRT they are using they should speak to their doctor."

Former Tory MP Teresa Gorman, who takes HRT, told the BBC the treatment had a proven track record of improving the quality of life of older woman.

Ms Gorman, who is over 70, has been told that she has the skeleton of a 15-year-old.

The former Tory MP for Billericay said: "It's absolute nonsense to scare women off this kind of treatment.

"My message to women is don't stop taking the tablets".