An investigation into the safety of hormone replacement therapy (HRT) has been launched by European watchdogs.
A major study has pointed to an increased risk
The probe, by the European Agency for the Evaluation of Medicinal Products, was sparked by a major study which pointed to increased cancer risks.
In theory, the agency has the powers to order some types of HRT - which relieves menopause symptoms - to be taken off the market.
Its experts are expected to report back before the end of the year.
The recent "million women study" published in The Lancet suggested that long-term users of certain types of HRT had double the risk of breast cancer.
Some governments have already taken action to limit the use of HRT as a result - in Germany, authorities say they will restrict it to women with the most severe menopausal symptoms, and at as low a dose and for as short a duration as possible.
The agency cannot launch an official probe without a request from a member government, and this has not been tabled, so this is an informal investigation.
If the panel of experts appointment by EMEA decides that HRT presents a "public health risk", then it can recommend that a formal investigation is launched.
Should that go ahead, it could take anything from a few months to well over a year.
However, the agency has sweeping powers to take pharmaceuticals off the shelves in every EU country.
It can also place restrictions on the use of drugs which are binding in every country.
Researchers estimated that HRT use caused 20,000 extra cases of breast cancer in the UK over the last decade in women aged 50 to 64.
Three-quarters of these could be blamed on "combined" HRT formulations - a mixture of the hormones oestrogen and progestogen.
Single hormone HRT based only on oestrogen presented less of a risk, the study found.
In the UK, at least 1.5 million women take HRT, and half of these are estimated to be taking "combined" versions.
EMEA spokesman Martin Harvey told BBC News Online : "We felt this was something that the agency couldn't just ignore, even though no-one has formally referred it to us.
"So if our panel think there are grounds for a formal investigation, our recommendation will be a hint to the members that this is needed."