Researchers have uncovered a new concern about hormone replacement therapy (HRT) which may lay to rest the long held belief among doctors that it is good for the heart.

A study by the trial group set up to monitor HRT has discovered that the drug increases levels of the fat triglyceride, which is a known risk factor for heart disease, particularly in women.

Despite this finding, the Postmenopausal Estrogen/ Progestin Intervention (PEPI) researchers still conclude that the estrogen content in HRT helps reduce heart disease in women. Observers have claimed that estrogen can reduce the risk of heart attack by up to 50 per cent.

However, the direct effects of HRT on the heart are still being studied by the Women's Health Initiative, and the results are five years away.

As it stands, the PEPI report throws up as many new questions as answers. The triglyceride effect could, for example, make HRT a far more dangerous option for diabetics, and the study fails to answer concerns that the drug could increase the risk of stroke.

The report, based on 875 healthy postmenopausal women given either a placebo or varying levels of HRT, did not investigate the other supposed benefits of the drug, such as its ability to slow the onset of osteoporosis.

Its findings also did not make any allowance for the fact that most women who take HRT tend to be more health conscious in the first place, and so the drug may be unjustifiably taking credit when good diet and exercise were responsible for any benefits.