GPT and amyotrophic lateral sclerosis: A variety of markers of muscle involvement has been investigated as potential prognostic biomarkers for ALS, including potassium,24, 25 creatine kinase,15, 24, 26 lactate dehydrogenase,24 myoglobin,15 troponin T,15, 27 AST, ALT,24 and creatinine.21, 25, 28, 29, 30