It has already been well established that the male sex steroid, testosterone, is an important regulator of muscle size. Now we showed that also the female sex steroid, estradiol, has a substantial regulatory role in muscles, says Academy Research Fellow Eija Laakkonen from the Gerontology Research Center at the University of Jyväskylä. These findings help to understand why menopausal women’s muscles get smaller and their muscle strength diminishes, Dr. Laakkonen explains. Skeletal muscle is important for whole-body metabolism. Therefore, these results are important when fighting against the elevated risk of metabolic diseases associated to aging. In total 24 pre- and postmenopausal women participated in this muscle research on middle-aged women. By applying a proteomics approach to investigate the protein content of the muscle and by taking into account the participants’ age, menopausal status and the use of estrogen-containing hormonal therapy, the researchers were able to identify 1,353 proteins and quantify 762 of them. In total 137 of the proteins were associated for the first time with skeletal muscle aging. This collaborative study between the researchers of the University of Jyväskylä and the University of Helsinki was recently published in Aging Cell. The research is part of the larger SAWEs twin study that is led by Docent Vuokko Kovanen from the Faculty of Sport and Health Sciences, University of Jyväskylä, and funded by the Academy of Finland and the Päivikki and Sakari Sohlberg Foundation.