In weighing up the appropriate form of medical treatment for any kind of condition, the key is whether a drug does more good than harm. The latest judgment to come under the microscope is the cost of the rejuvenating effects of hormone replacement therapy. For increasing numbers of women, HRT has provided relief from menopausal symptoms, caused when the ovaries stop producing the oestrogen hormone, such as hot flushes, night sweats and mood swings. Dealing with these enervating effects gives many women a chance to live a more normal life. The treatment also deals with one of the most dangerous long-term effects of the menopause: the weak bone condition osteoporosis. All this has been disrupted by headlines this week caused by a US team's decision to halt their huge research project on HRT.

Women in the US research have been taking a pill which combines oestrogen and progestin. The researchers have now concluded that the pill causes increases in breast cancer, heart attacks, stroke and blood clots. In percentage terms the relative risks look large; for example, there is a 26% increase in invasive breast cancer and a 41% increase in stroke risk. Yet when the absolute numbers are considered, the risk for individual women is less dramatic. The research found that among the 10,000 women in the survey there would be an extra eight cases of breast cancer, eight strokes and seven coronary heart disease events a year. The tablet used in the US study is not available here, but its nearest equivalent is taken by about 300,000 British women, suggesting a potential 240 occurrences of breast cancer linked to the treatment.

The increased risk should not be exaggerated, but it is vital not to underplay the study's findings either. This is the first definitive proof that HRT increases the chance of heart disease. However the increased risk is comparable, say doctors, to the risk from being overweight. The new findings mean doctors and patients will have to consider more carefully whether to take HRT. Just because the therapy could transform a woman's life may not outweigh the risks for some women. For most, stronger evidence that HRT's risks outweigh its benefits is needed before considering whether to abandon the treatment. Proper assessment of the risks without needless alarm is essential. Despite the real concerns raised by the study, the message to those on HRT should remain: do not panic.