Progesterone-Alone for Hot Flashes and Night Sweats?

May 4, 2012

Many women going through perimenopause and in menopause either don’t have have flashes and night sweats that bother them or are able to ease them with self-help approaches.  However, between 7 and 9 percent of women have symptoms severe enough to interfere with their quality of life.

In the past, the primary treatment for hot flashes and night sweats (called vasomotor symptoms) was estrogen-plus-progestin or estrogen-alone hormone therapy—both effective therapies. But as the Women’s Health Initiative (WHI) trials demonstrated, these hormone regimens unfortunately increase the risk of heart disease, stroke, blood clots and breast cancer.

Because of these risks, new treatment options for vasomotor symptoms are needed. A new study published in the journal Menopause by the Centre for Menstrual Cycle and Ovulation Research looks at the safety and effectiveness of progesterone-only therapy for alleviating hot flashes and night sweats. (Progesterone is a hormone produced in the body, while progestin, which was used in the WHI, is a synthetic form of progesterone).

In this trial, the researchers randomized 133 healthy, postmenopausal women with vasomotor symptoms to Prometrium (a brand of oral micronized progesterone) or placebo, and had them report on the frequency and severity of their night sweats and hot flashes over three months.

The researchers (one of whom, Jerilynn Prior, co-wrote the menopause chapter in the 2011 edition of Our Bodies, Ourselves) found that symptoms improved in both the progesterone and placebo groups over the course of the study. Scores, however, improved significantly more in the progesterone group, suggesting that the hormone provided greater relief of symptoms than placebo. There were few adverse effects reported in this brief trial, none of which were considered serious.

It is not clear what the breast cancer implications of progesterone-alone therapy might be. The Women’s Health Initiative trials found an increased risk of breast cancer with estrogen-plus-progestin therapy but not with estrogen-alone. In their article, the authors briefly address this issue, noting varying findings in other studies and remarking that:

Although there is reason to believe that progesterone has a more favorable safety profile than medroxyprogesterone [used in the WHI study], large safety trials of progesterone as postmenopausal monotherapy are lacking.

OBOS contacted researcher Jerilynn Prior to ask her if she had any additional comments about the potential increased risk of breast cancer. Prior answered that a large observational study in France called E3N found that estrogen with progesterone was not associated with increased breast cancer risk, while estrogen alone and estrogen with progestin were. “This suggests that progesterone alone would be safe in terms of breast cancer risk,” Prior noted.

In the published study, the researchers address certain limitations of their work, including the racial/ethnic makeup of their study population (primarily white), and participants being overall leaner and healthier than the general population. Additionally, while the placebo was identical to the active drug and neither the researchers or women could guess by the look or feel of the pill which they were taking, over time 54% of those receiving progesterone and 60% of those getting placebo were able to correctly guess their group assignment. In correspondence with OBOS, Prior said that this was likely due to the fact that many of those taking progesterone experienced improvement in their sleep.

The researchers also note that their population were postmenopausal, having not menstruated for 1-10 years, so their findings are not applicable to women transitioning into menopause.

The bottom line is that progesterone-alone may be a useful treatment for relieving hot flash and night sweat symptoms of menopause, although more investigation is needed. Many of the benefit and harms of hormone therapy may turn out to depend on the type of hormone, who’s using it, in what form, when and for how long. We hope to see more studies on this in coming years.

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