Progesterone Cream: Good for Hot Flashes, Not Bones

Healthfacts, Nov, 1999 by Maryann Napoli

Many women are using topically applied progesterone cream to prevent the bone loss associated with menopause, but a new study found that this hormone has no protective effect on bone density after one year of use (Obstetrics & Gynecology, 8/99). Progesterone cream was found to provide significant relief from vasomotor menopausal symptoms, such as hot flashes. The findings, however, should be regarded as preliminary due to the small number of participant's and the need for long-term follow-up.

H. B. Leonetti, MD and colleagues at St. Lukes Hospital in Bethlehem, PA, randomly assigned 102 healthy women who were within five years of menopause to apply either progesterone cream (brand name: Pro-Gest) or a placebo cream (with no active ingredient). All were instructed to apply a quarter of a teaspoon of cream to the skin each day. Those taking the progesterone cream were applying 20 mg of the hormone drug daily. A complete history, physical examination, bone density measurement, and blood tests were given at the onset of the study. All were taking daily multivitamins and 1,200 mg of calcium. Every four months, the women were given bone scans and blood tests. Improvement in vasomotor symptoms was determined by the researchers who reviewed each participants weekly symptom diary.

After one year, the amount of bone loss in women applying progesterone cream was no different from that of the women applying placebo cream. Measurements were taken at the hip and spine. Eight women in the progesterone group experienced vaginal bleeding. "One year is not enough time to determine Pro-Gest's ability to prevent bone loss," said Jeff Wilson, PhD, spokesman for Astraea, Inc., Portland, Oregon. This study was funded by Astraea, Inc., a research and development company affiliated with Transitions for Health, makers of Pro-Gest. Dr. Wilson noted that Merck, whose drug, Fosamax, prevents bone loss, had to follow women for three years to prove this result. Insufficient funding, he said in a telephone interview, has thus far prevented the Pro-Gest research from continuing.

As for the vasomotor symptoms, only a minority of the study participants reported this as a problem; therefore, the pool of women who tested this effect was small. In the progesterone group, 25 of 30 women reported vasomotor symptom improvement, compared with five of 26 in the placebo group.

Pro-Gest can be purchased by mail order and at health food stores and chain pharmacies. A spokeswoman for Transitions for Health said Pro-Gest has been available for 20 years. Because the product is defined as a cosmetic by the FDA, the company did not have to prove safety and efficacy prior to marketing. Last year, a British study raised questions about Pro-Gest because very little progesterone was absorbed. Dr. Wilson said another Astraea-funded study explored this question and was published recently in the American Journal of Obstetrics and Gynecology. The study, conducted at the Oregon Health Sciences University, involved six women who applied Pro-Gest once a day for a two-week period and then twice daily for two more weeks. Blood levels of progesterone ranged from 1.5 to 3.3 ng/mL which the investigators conclude is similar to the amount of estradiol absorbed by women on the FDA-approved hormone patch.

Questions remain about Pro-Gest's ability to prevent bone fracture and to protect the uterus from estrogen therapy-induced endometrial cancer.