Oral micronized progesterone could be another way to treat hot flashes and night sweats endured by post-menopausal women.
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.
"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, Dr. Jerilynn Prior, professor, University of British Columbia, Vancouver, Canada.
"Vasomotor symptoms"-hot flashes (sometimes called hot flushes) and cc-are experienced by most women during the years around the final menstrual period.
In the most symptomatic women (at least 5-10pct) these symptoms disturb sleep, energy and quality of life, said Prior.
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.
The researchers 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.
The authors found that progesterone, in a 300-milligram dose, was more effective than placebo at decreasing the intensity and number of symptoms, and the difference was both statistically significant and clinically important.
"Women improve very quickly on oral micronized progesterone. The improvement is apparent within the first 4 weeks," said Prior.
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," said Prior.
The results will be presented at The Endocrine Society's 92nd Annual Meeting in San Diego.