Analysis of hormone levels in older men in Sigapore suffering from sarcopenia showed that both dysregulated insulin/ghrelin and testosterone are responsible for muscle wasting. The full text of the article is online.
"Insulin signaling and energy metabolism (ISEM: denoted by insulin, C‐peptide, leptin). Based on present evidence, it remains unclear whether increased insulin resistance or reduced endogenous insulin secretion (or both) is underlying mechanisms in sarcopenia and frailty. Our result shows that low fasting plasma insulin and C‐peptide (a better measure of portal insulin secretion) levels are associated with low muscle mass and function and suggests that in this Asian group, endogenous reduction of insulin level and dysregulated insulin signaling activity in older individuals (with and without diabetes) diminish the anabolic capacity of insulin to alleviate muscle protein breakdown in skeletal muscles."
"Anabolic sex steroid regulation (ASSR: free testosterone, leptin). Next to insulin–leptin signaling and energy metabolism, ASSR appears to occupy a co‐pivotal role in the multiple hormonal dysregulation in sarcopenia. ASSR is inversely linked to ISEM, reflecting what is known about their complementary actions in protein synthesis and muscle accretion. Taken together, dysregulated anabolic and catabolic pathways via insulin signaling and energy metabolism and anabolic sex steroid regulation appear to be primary pathophysiological mechanisms directly related to the development of sarcopenia. "
"Insulin signaling and energy metabolism (ISEM: denoted by insulin, C‐peptide, leptin). Based on present evidence, it remains unclear whether increased insulin resistance or reduced endogenous insulin secretion (or both) is underlying mechanisms in sarcopenia and frailty. Our result shows that low fasting plasma insulin and C‐peptide (a better measure of portal insulin secretion) levels are associated with low muscle mass and function and suggests that in this Asian group, endogenous reduction of insulin level and dysregulated insulin signaling activity in older individuals (with and without diabetes) diminish the anabolic capacity of insulin to alleviate muscle protein breakdown in skeletal muscles."
"Anabolic sex steroid regulation (ASSR: free testosterone, leptin). Next to insulin–leptin signaling and energy metabolism, ASSR appears to occupy a co‐pivotal role in the multiple hormonal dysregulation in sarcopenia. ASSR is inversely linked to ISEM, reflecting what is known about their complementary actions in protein synthesis and muscle accretion. Taken together, dysregulated anabolic and catabolic pathways via insulin signaling and energy metabolism and anabolic sex steroid regulation appear to be primary pathophysiological mechanisms directly related to the development of sarcopenia. "
