The cancer-causing potential of the sex hormones used in hormone replacement therapy has been known since the 1930s, researchers said today.
In the last few years a number of major studies have linked HRT used to combat menopausal symptoms to an increased risk of breast cancer and also stroke.
The revelations led many women to abandon treatment due to fears they faced a much greater risk of cancer.
Now researchers from the US have questioned why the results of the recent studies have been seen as so shocking when the potential dangers of hormone treatments have been known about for decades.
Writing in the Journal of Epidemiology and Community Health, they outlined the results of a meeting of historians, doctors, biologists and women’s health advocates to discuss the recent reaction to the HRT studies.
Controversy about the use of hormones in medicinal treatments has existed since the 1930s.
Back then scientists carried out animal experiments which provided evidence that sex hormones could be carcinogenic causing cancer.
“For clinicians, these studies translated to debates about the correct dose to be given, as hormones were viewed as ‘natural’ and thus not intrinsically harmful,” the team from the Harvard School of Public Health in Boston said.
Further controversy arose in the 1960s and 1970s, triggered by new fears about oral contraceptives, oestrogen only HRT and the risk of endometrial cancer.
New concerns are currently being discussed about the cancer-causing potential of HRT, and disputes over whether it does or does not reduce the risk of cardiovascular disease.
The researchers said the conventional wisdom was that the latest concerns were new concerns, only recognised in the last few years with the publication of major trials.
They said the question that needed to be answered was: “Why, for four decades, since the mid-1960s, were millions of women prescribed powerful pharmacological agents already shown, three decades earlier, to be carcinogenic?”
The researchers questioned why repeated warnings were ignored and not translated into health policies to protect women.
They suggested that the pharmaceutical industry, doctors and researchers “colluded” to promote the view that the menopause was a “deficiency disease” and women needed long-term HRT to “prevent illness, loss of sexuality and ugly ageing”.
The researchers said: “Use of drugs shifted from being ‘curative’ to being a tool of ‘risk management’, requiring long-term administration to an ever-expanding – and hence profitable – market of ageing users.”
They also said that other factors that played a part in the problem included the failure of regulatory agencies to act and too much focus on individual risk rather than broader societal issues.
The researchers claimed that hormones had been “gendered” with treatment targeted at women and their reproductive capacity – in a bid to regulate their sexually.
In contrast, men had been ignored in creating these treatments. Last week research in the British Medical Journal suggested that a woman’s risk of developing breast cancer while on HRT may be lower than people think.
The Australian researchers said that many women may have stopped taking HRT unnecessarily.
Hazel Nunn, cancer information officer at Cancer Research UK, said: “HRT remains an effective treatment for menopausal symptoms and may also lessen the risk of osteoporosis.
“Taking HRT slightly increases a woman’s risk of developing breast cancer while she is taking it, but risk returns to normal around five years after she stops.
“Cancer Research UK feels it is important for women to be aware of the risks of taking HRT and should discuss their individual circumstances with their doctor so that they can make an informed decision.
“We also recommend that women take HRT for only as long as it is necessary to combat their symptoms.”