I think it has benefits but women using HRT long-term should ask whether they are on the right compounds

Mike Dixon, consultant surgeon

This affects the sensitivity of breast screening because its effectiveness depends on the decreasing breast density normally seen with age.

Because breast tumours are made of relatively dense tissue, the bigger the difference between them and the rest of the breast, the easier they are to spot.

Mr Dixon believes in countries where HRT is widely used, the reduction in sensitivity of breast screening could undermine the capacity of national breast screening programmes to reduce deaths due to breast cancer.

Early HRT studies reported an increased risk of breast cancer for each year of use.

More recent studies have reported significantly higher levels of risk in women taking combined hormone preparations, compared with women taking oestrogen alone.

But Mr Dixon, a consultant surgeon at Western General Hospital, Edinburgh, is not suggesting women should stop taking HRT.

Further research

He said: "I think it has benefits but women using HRT long-term should ask whether they are on the right compounds.

"This is not a time for panic, this is a message to doctors.

"HRT is not the panacea we thought it was but for specific women it improves their quality of life no end."

Mr Dixon, whose comments are published in the British Medical Journal (BMJ), says specialists may have to look at different ways of screening post-menopausal women for breast cancer.

Breast screening is offered to post-menopausal women

Another option would be to encourage women to stop taking HRT a few weeks before their screening appointment.

But he insists further research is essential to understanding HRT's effects on breast density and cancer risks.

The Amarant Trust, which promotes greater understanding of the menopause fears women will turn their backs on HRT as a result of Mr Dixon's comments.

Amarant Trust deputy director Val Godfree said: "This is one doctor's expert opinion.

"We tell women what the downsides of HRT are and there is some risk involved with breast cancer, but it only goes up by two per thousand women after five years continuous use."