A new analysis of the data to date suggests some previously seen benefits haven't passed the test of time, but some risks haven't either.
Still, the bottom line seems unchanged: for most women, there isn't a good medical reason for taking estrogen preparations after menopause to prevent development of chronic illnesses or bone fractures.
That doesn't mean the drugs don't have a role to play in treatment of the symptoms of menopause — the debilitating hot flashes, night sweats, joint pain and insomnia some women suffer when they go through what's euphemistically called The Change.
But while expert panels in both Canada and the United States are currently reviewing their advice on HRT, it seems the standing recommendations — take the drugs at the lowest effective dosage for the shortest time possible — are unlikely to change.
"If we just look at the data, we don't see a lot of compelling benefit," Dr. Heidi Nelson, lead author of the review, said of the once-popular notion that post-menopausal women could use hormone therapy to stave off a number of age-related conditions including bone fractures, heart disease and cognitive decline.
The review, published in the journal Annals of Internal Medicine, was done to help the U.S. Preventive Services Task Force to update its recommendations on post-menopausal use of hormone therapy. That body's updated guidance is expected to be released shortly.
The Society of Obstetricians and Gynecologists of Canada is in the process of updating its recommendations on HRT use, said Dr. Robert Reid, a former president of the organization.
The Canadian Task Force on Preventive Health Care has not revisited its advice on HRT since 2003, shortly after a massive study of hormone use — the Women's Health Initiative — reported that rather than improving women's health, hormone therapy appeared to put them at greater risk of developing invasive breast cancer, strokes and heart disease.
The 2003 guidance suggests hormone replacement shouldn't be used for disease prevention; women who want to use it for menopausal symptoms should review their risk-benefit profiles with their doctors.
But those discussions have been tough, experts say. Interpreting the pros and cons of hormone replacement is a complicated business, and the passage of time hasn't necessarily made it simpler.
"It's a more difficult decision now, because we do know there are harms. It hard to know how that applies to the person sitting in front of you," said Nelson, an internal medicine specialist at the Oregon Health and Science University in Portland.
For instance, longer term follow up of women who took part in the studies included in the review shows that HRT use does not reduce the risk of colorectal cancer, as was earlier thought.
Likewise, the cardiovascular risks that led organizers to end the Women's Health Initiative early have washed out with time. When women who took HRT are compared to women who didn't, there is no longer a statistically significant increased risk of cardiovascular events seen, Nelson said.
However, the data continue to suggest women who take HRT are at an increased risk of having a stroke.
And the risk of breast cancer — foremost in the minds of many women who stopped using hormone replacement — is not a simple thing to describe.
For women who used estrogen plus progestin (the formulation of hormone therapy prescribed to women who have a uterus), the accumulated studies suggest a small increased breast cancer risk. You would expect to see 30 cases of invasive breast cancer per every 10,000 women in a single year in women who don't take HRT. In women who do, the number of invasive breast cancer cases would be 38.
But in women who have had a hysterectomy and take estrogen-only HRT, the treatment appears to have the protective effect — eight fewer invasive breast cancers per 10,000 women in a single year. (Women who have a uterus cannot take estrogen alone, because it increases their risk of developing endometrial cancer, cancer of the lining of the uterus.)
In the wake of the first report from the Women's Health Initiative, hormone therapy use plummeted. In the years since, it has slowly regained favour in some quarters, but for the treatment of difficult menopause symptoms, not chronic disease prevention, said Reid, who is chair of the division of reproductive endocrinology and infertility at Queens University in Kingston, Ont.
Still, some women who could benefit from treatment may not be getting it, he suggested.
"I think there's potential that the confusion that surrounded the initial release of the findings has distorted the medical profession's perception of hormone therapy, to the point where many family doctors are afraid to even discuss it now or they find it too confusing to try to discuss with patients," Reid said.
"And the lay public has had this fear of heart disease and stroke and breast cancer blown out of proportion."
He said women who consume two alcoholic drinks a day or who are overweight have the same level of increased risk of developing breast cancer as do women who use hormone replacement, but in general people don't perceive the risks to be equal.
"People accept these other risks in the lifestyle, but they panic when they think about hormones could cause these same kinds of risks," he said.