Definition Muscle Metabolism Muscle metabolism –> creatine –> creatinine (nonenzymatically converted). Creatinine production is constant, related to muscle mass (20-25 mg/kg males, 15-20 mg/kg females). Filtered but not reabsorbed in kidneys. Therefore, directly related to muscle mass, inversely related to glomerular filtration. More reliable than BUN because body muscle mass is fairly constant for a […]