Hormone therapy and skeletal muscle strength: A meta-analysis

Background. Our objective was to perform a systematic review and meta-analysis of the research literature that compared muscle strength in postmenopausal women who were and were not on estrogen-based hormone therapy (HT). Methods. Twenty-three relevant studies were found. Effect sizes (ESs) were calculated as the standardized mean difference, and meta-analyses were completed using a random effects model. Results. HT was found to result in a small beneficial effect on muscle strength in postmenopausal women (overall ES = 0.23; p =.003) that equated to an ∼5% greater strength for women on HT. Among the 23 studies, various muscle groups were assessed for strength, and those that benefitted the most were the thumb adductors (ES = 1.14; p < .001). Ten studies that compared muscle strength in rodents that were and were not estradiol deficient were also analyzed. The ES for absolute strength was moderate but not statistically significant (ES = 0.44; p =.12), whereas estradiol had a large effect on strength normalized to muscle size (ES = 0.66; p =.03). Conclusion. Overall, estrogen-based treatments were found to beneficially affect strength.