This week's US research results support previous findings that long-term HRT use can cause breast cancer and blood clots. But short-term treatment to relieve menopausal symptoms is still beneficial, writes Dr Muiris Houston, Medical Correspondent
For the millions of women worldwide who take hormone replacement therapy, this week's announcement of major research results calling into question its safety in long-term use will have come as quite a shock.
The concept of using oestrogen as a prophylactic treatment for menopause symptoms was first mooted in the early 1930s. However, it was the mid-1950s before HRT became commercially available in the US and Britain. Doctors prescribed oestrogen on its own until the first HRT "scare" in 1975, when the New England Journal of Medicine highlighted the increased risk of cancer of the womb in women receiving oestrogen replacement therapy.
Thereafter, progestogen, another female hormone, was added to protect the womb from this risk, resulting in the combined oestrogen and progestogen product prescribed for the majority of patients today.
A combined product first received a licence in the Republic in 1983, but it is really only in the last decade that HRT has been widely prescribed and used.
It is estimated that between 10 and 12 per cent of women over the age of 50 take HRT.
To some observers, its popularity has been due to the "medicalisation" of the menopause. There are different schools of thought as to whether the menopause is a disease or not.
One sees the menopause as a collection of symptoms which can be treated and as an opportunity to prevent long-term health consequences.
Another embraces it as a natural event, uneventful for most women. The Japanese do not share the concept of "the change of life" and the end of menstruation has little cultural significance.
But for many women in the Western world, HRT has transformed their lives and given renewed vitality. So what are the implications arising out of this week's announcements?
The Women's Health Initiative is a large-scale study of the long-term effects of combined HRT. Of 16,000 US women, half were given a daily tablet of oestrogen and progestogen. The rest were given a matching placebo, or "dummy" pill. Those on a daily dose of 0.625mg of conjugated oestrogen plus 2.5 mg of medroxyprogesterone acetate were found to be at increased risk of breast cancer, heart attacks, strokes and blood clots.
Although the relative risk of these side-effects expressed in percentages is alarmingly high, the actual risk to individuals is quite low. If 10,000 women took this form of HRT for a year, seven would suffer a heart attack, and eight a breast cancer which could be attributed to the medication. It is this statistic that women should focus on as they make decisions about continuing with HRT.
Another reassurance is that the particular type of HRT used in the study is not marketed in the Republic. The closest product to it is Premique, which is a trade name, which has a slightly higher dose of progestogen than the American drug.
Many women take HRT with different ingredients and different formulations to which these findings do not exactly apply, although there must now be some concern about the long-term effects of all forms of the medication.
As the dust settled following the initial announcement, experts here were emphasising that the research findings revealed relatively little new information, but largely confirmed existing knowledge.
Asked what advice she would give patients, Dr Ailís Ní Riain, director of women's health at the Irish College of General Practitioners, said: "HRT continues to be safe for short-term treatment of menopausal symptoms and a reasonable option for osteoporosis prevention. Women who are concerned about longer-term use should contact their own GP for further advice."
The Irish Medicines Board, following consultation with its EU counterparts, said: "The new information implies that long-term HRT with oestrogen plus progestogen, and likely other types of HRT, purely for the prevention of chronic disease, should not be generally advised. Short-term treatment of menopausal symptoms has a documented benefit that in most women should outweigh any of the risks."
Significantly, it added that the results of the study do not support the need for patients to discontinue HRT treatment.
Advising women to see their doctor every six months when taking HRT and to review the risks and benefits at each consultation, Dr Ní Riain said: "This paper changes nothing for the majority of Irish HRT users who take it for a relatively short period of time to relieve menopausal symptoms.
"Women who are already taking HRT can be advised that there is no immediate danger and that they can continue using their current preparation until they are due for review by their prescribing doctor.
"Women should not consider starting or continuing HRT if the only indication is a risk of cardiovascular disease."
Essentially, the WHI study supports existing information that long-term HRT use can cause breast cancer and blood clots.
The finding of an increased rate of coronary heart disease signals the death knell for previous suggestions that HRT could prevent heart disease and strokes.
Long-term usage still prevents osteoporosis, but women may want to consider other options to achieve this.
And for those who want to use HRT in the short term to relieve menopausal symptoms, the message is: this study changes nothing.