Age-related decline in testosterone is known to be associated with various clinical symptoms among older men and it is possible that the accompanying decline in muscle mass and strength might lead to a decline in motor and physical functions. Sarcopenia is an important pathophysiological factor associated with frailty in older adults and is diagnosed in older adults as a decrease in muscle strength, muscle mass, and walking speed, which can lead to a significant decline in the quality of life and shortened healthy life expectancy. Testosterone directly interacts with the androgen receptor expressed in myonuclei and satellite cells and is also indirectly associated with muscle metabolism through various cytokines and molecules. Currently, significant correlations between testosterone and frailty in men have been confirmed by numerous cross-sectional studies. Many randomized control studies have also supported the beneficial effect of testosterone replacement therapy (TRT) on muscle volume and strength among men with low to normal testosterone levels. In the world's aging society, TRT can be a tool for preventing the onset of sarcopenia in older-adult men. This narrative review aims to show the relationship between the decline in testosterone with age, sarcopenia, and frailty, as well as the effects of testosterone replacement therapy on muscle mass and strength.
Keywords: frailty; muscle; sarcopenia; testosterone.