What’s the correlation between AST, ALT, ALP and GGT?

• 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.

Normal levels:

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
  • Medications
  • 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,
• pregnancy,
• chronic renal failure,
• lymphoma,
• congestive heart failure.

Limitations:

• 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.

References:

• https://www.banglajol.info/index.php/DMCJ/article/view/22234
• https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_Diabetes_Guide/547086/all/Liver_function

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