Hormone replacement therapy (HRT) significantly improves muscle function in postmenopausal women, according to a new study.

The research showed that muscle function in these women improves down to the muscle fiber level. The finding was published in The Journal of Physiology.

Over the last 10 years, the negative results of several HRT studies put many women off.

However, the results of this new report have shown a positive outcome from HRT – a treatment which can relieve symptoms of menopause.

Past studies which have observed walking speed and jumping height have indicated that the treatment decreases the effects of age-related decline in muscle mass and strength. For the first time, these effects have been examined at cellular and molecular levels in this study.

Six pairs of postmenopausal identical twins were involved in the investigation. In order to rule out genetic differences, only one pair of each set of twins underwent HRT. The experts then closely observed muscle biopsies taken from the subjects.

Leading researcher Dr Lars Larsson, from Uppsala University Hospital Sweden, said:

“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.”

HRT is also linked to a more efficient organization of myonuclei – crucial components for the function of muscle fiber.

In females who use HRT, the different myonuclei arrangement makes the most effective use of cellular level protein transport that results in improved muscle function.

Elderly people are more susceptible to falls, and injuries caused by falling down. Such injuries place a significant socioeconomic burden on society and individuals. Older females are more severely affected than older males, because the reduction in the production of female sex hormones weakens their bones and muscles more severely. Dr Larsson concluded:

“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.”

The authors believe their study demonstrates the potential for pharmacological interventions, aimed at improving muscle mass and function in older adults, which would improve not only overall health, but also quality of life.

Last year, a study showed that women who receive HRT soon after menopause have a much lower risk of heart attack, heart failure or dying early compared to females of the same age who do not.

Written by Sarah Glynn