- ALT and AST are abundant liver enzymes.
- AST is also present in heart, muscle.
- ALP is present in nearly all tissues, primarily bone and liver.
- GGT is abundant in liver, kidney, pancreas and intestine.
ALT and AST normal ranges vary depending on lab, in general: ≤ 40 U/L.
Mild ALT and AST elevations:
(ALT and AST less than 5 times the upper limit of normal)
–> Should be rechecked before extensive work-up is undertaken.
- Possible causes:
- Chronic hepatitis C or B
- Acute viral hepatitis
- Nonalcoholic Fatty Liver Disease
- Hemochromatosis (iron disorder)
- Autoimmune hepatitis
- Alcohol-related liver injury
- Wilson’s disease
Moderately elevated ALT and AST:
(ALT and AST 5-15 times the upper limit of normal)
–> Should be investigated without waiting to confirm the persistence of abnormal ALT.
- Possible causes:
- entire spectrum of liver diseases that may cause either mild or severe elevations.
Severe ALT and AST elevations:
(ALT and AST greater than 15 times the ULN)
Suggest severe acute liver cell injury:
- acute viral hepatitis
- ischemic hepatitis or other vascular disorder
- toxin-mediated hepatitis
- acute autoimmune hepatitis
Elevated ALP and GGT:
- Bile duct obstruction,
- primary biliary cirrhosis,
- primary sclerosing cholangitis,
- benign recurrent cholestasis,
- infiltrative disease of the liver (sarcoidosis, lymphoma, metastasic disease)
Isolated high ALP (extra-hepatic disease):
- bone disease,
- chronic renal failure,
- congestive heart failure.
- Poor correlation between ALT and AST levels and hepatic fibrosis (=overly exuberant wound healing in which excessive connective tissue builds up in the liver).
- Patients with cirrhosis may have normal or only mildly elevated ALT.
- ALT and AST: increase with strenuous exercise and muscle injury.
- Meals have no effect.
- ALT is increased with higher BMI.
- ALP levels increase with food intake, pregnancy and smoking.
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