University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

379

Pages:

2
Author:

Mariam A. A.

• • • • • • • • • • Hepatocellular injury Both aspartate aminotransferase (AST) and alanine aminotransferase (ALT) are normally present in serum at low levels, usually less than 40 U/L ALT is present in several organs and in muscle however the highest levels are in the liver which makes this enzyme a more specific indicator of liver injury Both AST and ALT are released into the blood in greater amounts when hepatocytes are damaged o Elevations of the AST level may also be seen in acute muscle injury, cardiac or skeletal muscle o ALT has a cytosolic form while AST has both cytosolic and mitochondrial forms Hepatocyte necrosis in acute hepatitis, toxic injury or ischemic injury → leakage of enzymes into circulation Chronic liver disease (hepatitis C, cirrhosis): serum ALT level correlates only moderately well with liver inflam Patients with cirrhosis often have normal or only slightly elevated serum AST and ALT levels → AST and ALT lack some sensitivity in detecting chronic liver injury AST and ALT levels tend to be higher in cirrhotic patients with continuing inflammation or necrosis than in those without continuing liver injury Dialysis patients: for both AST and ALT, the average values and upper limits of normal in patients undergoing renal dialysis are about one half of those found in the general population Very high ALT levels: o ALT levels often rise to several thousand units per liter in patients with acute viral hepatitis. o Highest ALT levels (often more than 10,000 U per L) are usually found in patients with acute toxic injury subsequent to acetaminophen overdose or acute ischemic insult to the liver o AST and ALT levels usually fall rapidly after an acute insult Death cap mushrooms – Amanita phalloides damages liver → hepatic failure • • • • Rhabdomyolysis (skeletal muscle injury → breakdown of muscle tissue) o Patients with rhabdomyolysis can have markedly elevated creatine kinase (CK) + high ALT and AST o If a patient has very high ALT and AST but normal bilirubin and ALP consider rhabdomyolysis and order creatine kinase Lactose dehydrogenase (LDH) o Less specific than AST and ALT as a marker of hepatocyte injury ▪ LDH is disproportionately elevated after an ischaemic liver injury Typical population distribution of aminotransferase: Causes of elevated ALT or AST values in asymptomatic patients o A: autoimmune hepatits o B: hepatitis B o C: hepatitis C o D: drugs or toxins o E: ethanol o F: fatty liver o G: growths i.e. tumours o H: haemodynamic disorder (congestive heart failure) o I: iron (haemochromatosis), copper (Wilson’s disease), alpha-antitrypsin deficiency o M: muscle injury