Serum alanine aminotransferase in skeletal muscle diseases

Abstract

Although elevation of the levels of serum alanine aminotransferase (ALT) following liver injury is well known, confusion exists concerning skeletal muscle injury as the cause of this rise. We reviewed the records of 16 patients who had muscle necrosis without evidence of liver disease. The patients were divided into three groups: extreme exercise, polymyositis, and seizures. All patients exhibited markedly elevated creatine kinase and lactate dehydrogenase levels consistent with muscle injury. In acute cases, aspartate aminotransferase (AST) and ALT were both elevated, and the AST/ALT ratio was greater than 3, but this ratio approached 1 after a few days because of a faster decline in AST. In conclusion, this difference in half-life accounts for the comparable AST and ALT levels in our cases with chronic muscle injury. (HEPATOLOGY 2005;41:380-382.)

Elevated Liver Enzymes Indicating a Diagnosis of Limb-Girdle Muscular Dystrophy

“…The ALT was found to fall at a lower rate given its longer half-life (the half-life of AST is 17±5 h, while that of ALT is 47± 10 h). 7,13 No significant elevations were found in INR, suggesting that the elevations in AST and ALT were likely from muscle damage alone. Another study looked at liver function testing in patients known to have myotonic dystrophy and showed significant elevations in patients who had a normal liver, were free of medications, and not pregnant.…”

“…Elevated transaminases have been observed in various myopathies, hyperthyroidism, and celiac disease and even used as a marker for myocardial infarction. [7][8][9][10] In fact, due to the larger proportion of skeletal muscle, adult males have four times more ALT and 26 times more AST on average in their muscle than in their liver. 11 The association of AST and ALT release during muscle damage is well known.…”

Spectrum of NAFLD and diagnostic implications of the proposed new normal range for serum ALT in obese women

“…The light absorption that is lost when NADH is oxidized to NAD (during pyruvic acid conversion to lactate) is used to indirectly measure ALT (and AST) activity. Although ALT activity is mostly hepatic in origin, muscle inflammation 18 or injury 19 can increase serum ALT. Elevated liver enzymes often correlate poorly with the degree of the chronic liver injury, 20 steatosis, and fibrosis.…”

Update on Advances in Research on Idiosyncratic Drug-Induced Liver Injury

“…ALT activity can also increase from other extrahepatic injuries, such as skeletal muscle injury due to inflammation. 85 Serum alkaline phosphatase is not liver-specific and can be increased in other disease states. 84 Total bilirubin is an insensitive marker of liver disease.…”