Oral micronized progesterone effective for women with symptomatic hot flashes

Postmenopausal women who experience bothersome hot flashes or night sweats may have an alternative treatment to estrogen. According to a new study, oral micronized progesterone relieves those symptoms. The results will be presented Saturday at The Endocrine Society's 92nd Annual Meeting in San Diego.

"This is the first evidence that oral micronized progesterone, which is molecularly identical to the natural hormone, is effective for women with symptomatic hot flashes," said the presenting author, Jerilynn Prior, MD, professor, University of British Columbia, Vancouver, Canada.

Available only by prescription and sold under the brand name Prometrium in the United States and Canada, this form of progesterone is manufactured from a steroid in yams.

"Vasomotor symptoms"—hot flashes (sometimes called hot flushes) and night sweats—are experienced by most women during the years around the final menstrual period. In the most symptomatic women (at least 5-10%) these symptoms disturb sleep, energy and quality of life, Prior said.

The researchers recruited 114 healthy postmenopausal women seeking hormonal therapy for hot flashes and night sweats and randomly assigned them to take either oral micronized progesterone or an inactive substance (placebo), both as three round capsules at bedtime. Neither the women nor the study team members were aware which treatment the study participants received during the three months of therapy. The time since their last menstrual flow was one to 10 years, with an average of four years. To be eligible to participate in the study, women could not have taken ovarian hormone therapy within the past six months.

Prior and Christine Hitchcock, PhD, of the University of British Columbia, calculated the average daily vasomotor symptom score, or VMSScore, from the data that subjects recorded in a daily diary. This score reflects both intensity and number for hot flashes and night sweats each day.

Progesterone, in a 300-milligram dose, was more effective than placebo at decreasing the intensity and number of symptoms, the authors reported, and the difference was both statistically significant and clinically important. The 68 women taking progesterone showed a 56% improvement from baseline in VMSScore, and a 48% reduction in the number of VMS; the 46 women taking placebo had 28% lower VMSScores and a 22% reduction in number.

"Women improve very quickly on oral micronized progesterone. The improvement is apparent within the first 4 weeks," Prior said.

Micronized progesterone did not cause any serious side effects, she said. The drug may be an option for postmenopausal women who do not want to or should not take estrogen—"currently the only effective therapy for decreasing severe vasomotor symptoms," Prior said.