Testosterone and progesterone, but not estradiol, stimulate muscle protein synthesis in postmenopausal women.

Context: The effect of the female sex steroids, estradiol and progesterone, on muscle protein turnover is unclear. Therefore, it is unknown whether the changes in the hormonal milieu throughout the life span in women contribute to the changes in muscle protein turnover and muscle mass (eg, age associated muscle loss).

Objective: The objective of this study was to provide a comprehensive evaluation of the effect of sex hormones on muscle protein synthesis and gene expression of growth-regulatory factors [ie, myogenic differentiation 1 (MYOD1), myostatin (MSTN), follistatin (FST), and forkhead box O3 (FOXO3)].