Post-menopausal women may suffer fewer hot flushes and night sweats by taking the hormone progesterone, a Canadian study has found.
After 12 weeks of progesterone treatment, women who began the study with a daily average of seven hot flushes or night sweats reported having three fewer episodes each day.
The study is the first to show that oral progesterone may reduce frequency and severity of hot flushes and night sweats, says co-author Jerilynn Prior, an endocrinologist at the Centre for Menstrual Cycle and Ovulation Research at the University of British Columbia.
"I think this is important research because it offers women more choices," Dr. Prior says.
Conflicting information about estrogen therapy has left postmenopausal women wary of taking hormone treatments. In 2002, the Women's Health Initiative study linked estrogen treatments with a higher incidence of breast cancer, heart attacks and strokes. However, other studies have found that estrogen may prevent bone loss and decrease the risk of colorectal cancer if taken only for short periods.
The progesterone study, published in the journal Menopause, did not compare estrogen and progesterone treatments in a head-to-head trial. Nevertheless, Dr. Prior says progesterone is "as effective as estrogen but better at helping with sleep."
For the study, researchers recruited 133 healthy women aged 44 to 62 who hadn't menstruated for one to 10 years. More than half took 300 milligrams of progesterone each night while the rest took a placebo. All the women kept a diary to record the frequency and severity of hot flushes and night sweats before and during the treatment period.
Dr. Prior explains that hot flushes and night sweats are signs of the natural drop in estrogen as women go through menopause – the cessation of menstrual periods. As estrogen levels decrease, the body's comfortable temperature zone narrows until, for some women, "there's almost no temperature at which they're comfortable."
She theorizes that progesterone offers relief by raising core temperature and driving up the body's comfortable temperature zone.
Prescribing oral progesterone alone as a treatment for menopause symptoms is unusual in medical practices, notes Richard Santen, an endocrinologist at the University of Virginia.
The benefits of progesterone shown in the study are "statistically significant but not so great" compared with other treatments, particularly estrogen combined with progesterone, Dr. Santen says. Nevertheless, he says, "most physicians would consider it reasonably safe."
Christine Derzko, an associate professor of obstetrics and gynecology at the University of Toronto, cautions against the use of progesterone as a main treatment for menopause symptoms.
Dr. Derzko notes that many women suffer from vaginal dryness – a sign of lower estrogen levels. "If the problem is an estrogen deficiency, you give them estrogen," she says.
Dr. Derzko says she frequently prescribes oral progesterone for premenopausal women with sleep problems. But she argues that Dr. Prior's research doesn't prove that progesterone is an effective treatment for hot flushes aside from its sedative effect. "What we don't have here is a long enough study to show us that in the long term, it's a good treatment, it's a safe treatment."
But Dr. Prior says women in the study experienced fewer hot flushes throughout the day and not just while they were asleep.
Dr. Prior says while there is no data on the safety of long-term use of oral progesterone, they have been "well tolerated" in the 17 years she has been prescribing them to patients.
In the progesterone study, eight women taking progesterone and four women taking the placebo reported adverse events such as headaches, tiredness and an unexpected menstrual flow. All were mild events compared with the potentially serious side effects associated with estrogen therapy, notes Dr. Prior.
Alarm about estrogen therapy has left many postmenopausal women "suffering in silence," according to a statement from the Endocrine Society, based in Chevy Chase, Md. A recent poll commissioned by the society found that 72 per cent of women aged 45 to 60 experiencing hot flushes, interrupted sleep and vaginal dryness had not received treatment for their symptoms.
But it's possible that many women's symptoms are mild and do not require treatment, Dr. Prior says. She cites a 2008 study published in the journal Climacteric that involved 4,400 women aged 40 to 65. The study found that over all, just 9 per cent of premenopausal and 7 per cent of postmenopausal women reported hot flushes and night sweats that were "moderate" to "very severe" in a typical day.