Making sense of menopausal hormone therapy means understanding the benefits as well as the risks
At menopause, a woman's ovaries lose their reproductive function. Eggs are no longer released and the production of the hormones estrogen and progesterone falls. It's the lowered levels of estrogen after menopause that gives rise to troublesome postmenopausal symptoms.
Typical symptoms include hot flushes, night sweats, anxiety, low mood, disturbed sleep, joint pain and vaginal dryness. These symptoms can be debilitating.
The fall in estrogen also leads to bone loss and an increased risk of fragility fractures. And women going through menopause have increased central abdominal fat, even without an increase in weight. This contributes to a heightened risk of diabetes and heart disease.
An absence of symptoms doesn't mean bone loss and other metabolic changes aren't occurring, as these develop silently.
Menopausal hormone therapy (MHT) – which used to be known as hormone replacement therapy, or HRT—is the most effective treatment we have for menopausal symptoms. Yet many women and health-care providers remain confused about the benefits and risks of MHT.
What is menopausal hormone therapy?
MHT replenishes estrogen supplies in the body to treat the symptoms of menopause. Taking estrogen causes thickening of the lining of the uterus, so progestogen (which acts like progesterone) is added to MHT to stop this.
This is important because a thickened uterus lining may undergo cellular changes that have the potential to develop into uterine cancer. For a woman who has had a hysterectomy (surgery where the uterus is removed) MHT will be estrogen-only.
estrogen is usually taken in tablet form, but can be applied as a skin patch or skin gel, or as a vaginal pessary. Progesterone is taken as a capsule. There are a range of single formulations and combinations, so the dose and formulation of MHT should be tailored to each woman's health profile and personal preferences.
Women shouldn't take MHT if they have a malignancy sensitive to estrogen, like breast cancer, or have undiagnosed vaginal bleeding.
Unless there's a specific reason they can't, it's especially important women with early menopause take MHT to optimize their health. This is true regardless of how severe their symptoms are.
Menopause before age 45 is classified as early menopause. Prematurely menopausal women are at significantly greater risk of osteoporosis and fracture, heart disease and premature death.
For women going through menopause at the usual time, the choice may be less clear-cut.
Importantly, MHT cannot be seen in one dimension; that is, as only having one benefit or one risk. To make an informed choice, it's essential to evaluate the total effects of MHT, including how it influences the risk of premature death, heart disease, fracture, other cancers, and of course, well-being and quality of life.
Balancing the risks and the benefits
Clinical trials have found specific formulations of oral estrogen with progesterone result in a small increase in breast cancer risk. One study reported roughly a 1.25-fold increase in risk. This is equivalent to about four extra cases of breast cancer per 1,000 women per year in women who were taking this specific MHT formulation before and during the study period.
However, this risk estimate may be incorrect as the women in this study who had never used MHT prior to starting the study had no increased breast cancer risk compared with the placebo group. So some degree of uncertainty as to the risk remains.
There was no increase in risk for estrogen-only therapy, and whether these risks apply to non-oral therapies is not yet known.
These risks should be balanced with the benefits. Women who take MHT gain less abdominal fat and are less likely to develop diabetes.MHT prevents bone loss and therefore the risk of fragility fracture, an effect that continues after treatment is stopped. estrogen alone is associated with reduced heart disease risk, while estrogen plus progestogen also lowers the risk of colon and uterine cancer.
The most comprehensive summary of the safety of MHT is from the Women's Health Initiative study in which 27,347 participants were randomized to receive MHT or a placebo for five to seven years. The researchers followed up to see if death rates differed between women who had taken MHT compared with the placebo.
After 18 years, cancer mortality and death overall from any cause did not differ between the groups, irrespective of whether the MHT was oral estrogen-only or oral estrogen plus progestogen.
So if we add symptom relief to the equation, the benefits of MHT will outweigh the potential risks for most symptomatic women who start MHT within ten years of menopause (the time frame measured in this study).
Some women using MHT will continue on the treatment for five or ten years to manage their symptoms. More than 40% of women aged 60 to 65 still have hot flushes and night sweats, and one in seven of these women describe their symptoms as "severe".
The length of time a woman uses MHT for will depend on her symptom severity and individual needs, which should be re-evaluated alongside her risk profile every year with a health professional.
The alternatives aren't evidence-based
Claims over-the-counter or internet-purchased nutritional supplements or herbal tablets will "balance your hormones" and relieve symptoms cannot be substantiated.
Studies have consistently failed to show meaningful benefits of nutritional supplements or herbal tablets over placebo for hot flushes. And these treatments do not prevent bone loss or protect against heart disease.
Further, unproven therapies can also have side effects. Women considering herbal or naturopathic remedies should have a face-to-face consultation with a qualified therapist (as opposed to internet-based communication) to ensure their full symptom and health profile, as well as medication use, are documented to minimize adverse effects.