Hormone replacement therapy (HRT) is a hotly-debated and controversial topic in women’s health, but it is not without its benefits. Although the 2002 Women’s Health Initiative study reported that HRT was associated with an increased risk of breast cancer and heart disease, today's HRT researchers are uncovering important health benefits from HRT.

HRT has been found to help slow age-related decline in postmenopausal women's muscle mass and strength, reducing falls and improving mobility. Now, a group of Scandinavian researchers has examined the effects of HRT on muscle at the cellular and molecular level.

The findings could significantly impact the quality of life of postmenopausal women.

“We found that even though individual muscle fibers did not change in size, the muscles of HRT users showed greater strength by generating a higher maximum force compared to non-HRT users. It is thought that using HRT, at least in part, reduces modifications of muscle contractile proteins that are linked to aging, ” said study leader Lars Larsson in a statement.

The investigators enrolled six pairs of postmenopausal twins in their study; one twin from each pair took HRT and one did not. They found that HRT is associated with a more efficient organization of myonuclei, which are essential to the function of muscle fibers. This improvement in myonuclei arrangement means that single muscle fibers can generate more force without a change in size.

These findings could significantly impact the quality of life of postmenopausal women, according to the researchers. Falls and fall-related injuries are often why many older men and particularly women move to assisted living. Keeping women stronger longer can have a big impact on their quality of life.

“Future studies are focusing on the molecular mechanisms underlying the aging-related changes in skeletal muscle and the specific effects of HRT on the structure and function of the dominant protein in skeletal muscle, called myosin, which generates force and movement,” Larsson said. The research may help scientists develop medications that enhance muscle mass and function in old age, and ultimately enable seniors to live independently longer.

The study is published online in the Journal of Physiology.