Treatment with an ultralow-dose of the hormone estradiol, administered as a patch, reduces the rate of bone loss in older women without promoting the build-up of cells in the uterine lining, which is associated with an increased risk of cancer, according to a new report.

In older postmenopausal women, treatment with one quarter of the usual dose of estradiol improved bone mineral density (BMD) in the spine and the hip, but did not increase the build-up of cell in the lining of the uterus over a two-year period, lead author Dr. Bruce Ettinger, from Kaiser Permanente in Oakland, California, and colleagues report in the journal Obstetrics and Gynecology.

The findings are based on a study of 417 women, between 60 and 80 years of age, who were randomly assigned to receive an estradiol or placebo patch.

Treatment with the estradiol patch was associated with a doubling of hormone levels, whereas there was no change with the use of the placebo patch.

Lower spine BMD in the treatment group increased by almost three percent, a significantly greater increased than that seen in the placebo group. The total hip BMD increased by 0.4 percent in the estradiol group, but dropped by 0.8 percent in the placebo group.

Endometrial hyperplasia developed in one patient in the estradiol group and in none of those in the control group, the authors state.

Despite these encouraging findings, Ettinger’s team notes that “larger, long-term trials are needed to determine other potential benefits and harms of ultralow-dose estradiol therapy.”

Obstet Gynecol 2004;104.