Keywords: Sarcopenia, Low-T and Muscle Cell Loss, Muscle Cell Fiber, Muscle Hypertrophy, Testosterone and Muscle Size, Androgen and Muscle Cell, Weight Loss, Metabolism, Androgen Receptor, Muscle Growth, Low Testosterone and Muscle Wasting and Fatigue, Weight Gain, Gaining Muscle on Testosterone, Physical Function and Testosterone, SARMS
Men with low-testosterone (low-T) have decreased lean muscle mass compared to men with normal testosterone levels. The administration of testosterone to men with low-T results in an increase in lean muscle mass, muscle protein synthesis and enhanced fat cell (weight) loss.
The increase in muscle mass secondary to testosterone administration was first thought to be universal for all skeletal muscle in the human body; however, studies have found that muscles in the body respond differently to testosterone replacement (TRT). The muscles of the upper back, shoulders, head, and arms were most those most affected by testosterone and seemingly increase in size. The muscle of the thigh were not found be affected by testosterone as much. The exact mechanism why certain muscles are affected by androgen administration is unclear, but could relate to the hypothesis of different androgen receptor phenotypes in different muscle groups. Further research into this receptor variability within skeletal muscles could illicit androgens