Using progesterone for hot flashes shown safe for women's cardiovascular health

The findings, published today in PLOS ONE, help to dispel a major impediment to widespread use of progesterone as a treatment for hot flashes and night sweats, said lead author Dr. Jerilynn C. Prior, a professor of endocrinology and the head of Centre for Menstrual Cycle and Ovulation Research.

For decades, women used a combination of synthetic estrogen and progesterone to reduce the frequency and severity of hot flashes and night sweats, as well as to prevent osteoporosis. Use of this so-called "hormone replacement therapy" dropped dramatically after 2002, when a large study revealed that it increased risk of heart disease, breast cancer, strokes and other serious conditions.

To evaluate the cardiovascular risk of using progesterone to alleviate symptoms, Prior and her collaborators recruited 110 healthy Vancouver-area women who had recently reached postmenopause (a year after the final menstruation), giving half of them oral progesterone and the others a placebo for three months.

The team used each woman's age and changes in blood pressure and cholesterol levels to calculate their 10-year risk of a heart attack and other blood vessel diseases, and found no difference between those taking progesterone and the control group. The study also found no significant difference on most other markers for cardiovascular disease.

"Many women are apprehensive about taking progesterone for hot flashes because of a belief that it carries the same -- or even greater -- risks than estrogen," Prior said. "We have already shown that the benefits of progesterone alone have been overlooked. This study demonstrates that progesterone's risks have been overblown."

TREATMENT FOR HOT FLASHES AND NIGHT SWEATS

The change of life: The average age at which women have their final menstrual cycle is 51. Night sweats and hot flashes, caused by dramatic and unpredictable fluctuations of estrogen, usually appear in perimenopause (the years leading up to and a year beyond the final menstrual cycle) and usually continue into postmenopause.

An overlooked alternative? During the heyday of the combined "hormone replacement therapy," estrogen was considered the active ingredient in alleviating night sweats and hot flashes and preventing osteoporosis in later years. It was also considered effective in keeping women looking younger and more feminine. Progesterone was included mostly to guard against a thickening of the endometrium, the lining of the uterus, which could lead to uterine cancer. (Women whose uteruses had been removed by hysterectomy are usually given estrogen alone.)

The demise of estrogen: Though doctors still prescribe short-term estrogen for women with severe night sweats and hot flashes, it's not considered safe as a long-term prevention against osteoporosis or any other conditions of aging. Since estrogen use began to decline, breast cancer rates have started to fall; health statisticians believe the two trends are linked.

More studies underway: Prior, in contrast to many of her colleagues, has been prescribing progesterone since it became available in Canada in 1995, for postmenopausal women to treat flashes and night sweats, and for peri-menopausal women to alleviate hot flashes, heavy menstrual flow and sore breasts. In a randomized controlled study published in 2012, Prior and research associate Christine Hitchcock showed that progesterone significantly reduced the intensity and frequency of night sweats and hot flashes, compared to a placebo, in postmenopausal women. Prior is now recruiting Canadian women for a similar study examining progesterone's effectiveness for treating perimenopausal night sweats and hot flashes.