Menopausal hormone therapy (MHT) was popular in the 1990s before the publication of a study in the early 2000s saw its use rapidly plummet.
Today, having recovered from some misreporting around increased breast cancer risk, and with a better understanding of the study's findings among health professionals and women, the treatment is having a resurgence, says Susan Davis, head of the Women's Health Research Program at Monash University.
"I was a young doctor in this field in the '90s, and I feel like I'm reliving the '90s — except people aren't wearing shoulder pads."
Dr Davis says MHT, formally known as hormone replace therapy or HRT, is "the most effective way to relieve menopausal symptoms".
But like all medical treatments, she says there are risks to consider — and not everyone experiencing perimenopause and menopause needs to be on it.
What is MHT and what symptoms can it help with?
During perimenopause and menopause, changes in estrogen levels can cause a range of symptoms including hot flushes, night sweats, aches and pains, sleep disturbances and vaginal dryness.
Women and people who menstruate also report emotional and mental health impacts, such as depression, rage and brain fog.
MHT treatments contain estrogen, progesterone and sometimes testosterone, and are used to help alleviate these symptoms.
Different forms of MHT are available to treat different symptoms, and each come with their own benefits and risks, explains GP Lina Safro.
Dr Safro is on the board of the Australasian Menopause Society and chair of its education committee responsible for educating doctors and other professionals.
"When we talk about MHTs, there are a whole range of them — some are combined with both hormones [estrogen and progesterone], and others are purely estrogen."
MHT can be in the form of a topical cream applied to a specific area such as the vulva and vagina for those experiencing dryness, Dr Safro says.
"Then there is the MHTs we think of as systemic — which go to different areas of the body … that have receptors for those hormones.
"Those receptors are not just in the uterus or vagina, they are everywhere; the brain, different organs and tissues."
She says systemic MHTs usually take the form of either an oral pill, or a patch or gel.
In addition to treating menopause symptoms, MHT can also improve bone density and reduce the risk of fractures.
But what about the risk of breast cancer?
A Women's Health Initiative (WHI) study published in 2002 raised concerns about the safety of MHT, with media reporting including headlines such as "HRT causes breast cancer".
The study found MHT increased a woman's risk of heart disease and breast cancer, but Dr Safro explains participants already had established risks for both of these conditions.
More than 16,000 women were involved in the study, aged between 50 and 79, many of whom were "well past menopause", she says.
"In fact, 25 per cent of the women recruited were over 70 years old [and had] already established a risk for heart disease … [and] already established a risk for breast cancer."
Dr Davis says the study led to a dramatic decrease in medical professionals prescribing MHT, and women's willingness to take it.
It was later understood that the study was misleading.
"MHT became a no-go zone… and got to the point that if women were taking MHT they wouldn't tell their friends or family because the reactions were so severe," Dr Davis says.
Thanks to further research and a reanalysis of the 2002 data, Dr Safro says it is now clear that for women aged under 60 who use MHT, there is "an extremely small" increased risk of breast cancer.
Research suggests for combined MHT users, there would be an additional four cases per 1,000 women over the next five years.
Dr Safro says for women 60 and over, the risk of breast cancer from MHT is the same — but their risk is increased to begin with due to age.
"We would always discuss this with women requiring MHT over the age of 59, and explain that the added baseline risk plus the small added risk of MHT necessitates consideration.
"We also know for women who use estrogen alone, women with hysterectomy, there is no increased risk for breast cancer."
A 2019 review into MHT also found a small increased breast cancer risk with the use of MHT.
But Dr Safro says medical professionals no longer commonly prescribe the MHT used by women in the 2002 WHI study or the 2019 review, which was "very old, synthetic" estrogen and progesterone.
Dr Davis says today, there is more understanding from medical professionals and women about the risks associated with MHT and how it compares to other factors such as alcohol intake and weight.
"If you came to me as a patient and asked if MHT could increase your risk of breast cancer, I would say potentially yes, but compared to many other risk factors, it's extremely small."
Some forms of MHT can also increase your risk of blood clots, but for women with menopausal symptoms, the benefits of MHT are generally considered to outweigh the risks.
Dr Davis says MHT is "both over-prescribed and under-prescribed".
Earlier this year a group of Australian researchers argued that menopause is being over-medicalised and treatment options are too simplistic, narrow, and often swayed by commercial interests.
"There are women who really need it and would benefit who are not being given it," Dr Davis says.
"And there are women who are taking it because it's being promoted again [like in the '90s] as a bit of an 'elixir of youth'."
Who is MHT suitable for?
What type of MHT is suitable will depend on a person's age, whether they have a uterus, and what other health conditions they have, says Dr Safro.
For many women taking MHT, it will be a journey of "trial and error", she says.
"Many women will have different reactions to part of the MHT which is derived from progesterone."
Dr Safro says for this reason it's important medication is reviewed after a few months, and then at least every year following.
"As years pass, requirements change — there is no substitute for having a long-term follow-up with [a health professional] who is very interested and continually educated in this area."
For women without a uterus due to having a hysterectomy, she says MHT with only estrogen is suitable.
There are also some people for whom MHT is not suitable, such as those who have had hormone-dependent cancer (for example, breast cancer and some uterine cancers) or a history of blood clots. In these cases, other treatments including anti-depressants and non-hormonal drugs are available.
"Like in any other area of medicine, where we provide treatment to women, it's always a joint decision between the woman and the doctor," Dr Safro says.
Lifestyle modifications, such as maintaining a healthy weight and improving cooling through environmental control, "should not be discarded", she says.
While MHT is the most effective treatment available for menopause symptoms, Dr Davis says not everyone will need it.
"If a woman is fit, healthy, and has basically no symptoms, and has good bone health, I wouldn't be putting her on MHT."
This is general information only. For detailed personal advice, you should see a qualified medical practitioner who knows your medical history.
Editor's note, 18/11/24: An earlier version of this story said that 160,000 women were involved in the 2002 WHI study. While this is correct, the story has been updated to reflect that 16,000 were involved in the specific trial mentioned in this story.
