From the Guidelines
Elevations in both gamma-glutamyl transferase (GGT) and alkaline phosphatase (ALP) strongly suggest a liver or biliary tract origin, particularly cholestasis or biliary obstruction, as indicated by the most recent study on abnormal liver function tests 1. When evaluating liver function, GGT and ALP are crucial enzymes. GGT is primarily found in the liver, kidney, and pancreas, and its elevation typically points to liver disease or alcohol consumption. ALP, on the other hand, is present in the liver, bone, intestine, and placenta, with elevations suggesting biliary obstruction, certain liver diseases, or bone disorders.
- Key points about GGT and ALP include:
- GGT is not found in bone, making it useful for differentiating between liver and bone sources of elevated ALP.
- Elevated ALP with concomitantly elevated GGT confirms that the ALP elevation is of hepatic origin, indicating cholestasis 1.
- Normal GGT levels are typically below 30-50 U/L for men and 25-40 U/L for women, while normal ALP ranges from 44-147 U/L in adults, though reference ranges vary by laboratory.
- These enzymes are part of routine liver function tests, and abnormal results usually require further investigation with imaging studies like ultrasound or additional blood tests to determine the underlying cause. Given the information from the study on abnormal liver function tests 1, the presence of elevated GGT alongside elevated ALP is a strong indicator for further investigation into liver or biliary tract disease, such as choledocholithiasis, primary biliary cholangitis, or drug-induced cholestasis, to determine the etiology of the elevation and appropriate management.
From the Research
GGT and Alk Phos Relationship
- GGT (gamma-glutamyl transpeptidase) and Alk Phos (alkaline phosphatase) are two liver enzymes that are often elevated in patients with liver disease 2, 3, 4, 5.
- Elevated Alk Phos levels are associated with cholestatic liver disease, such as primary biliary cholangitis (PBC), while elevated GGT levels are associated with a variety of liver diseases, including PBC, alcoholic liver disease, and non-alcoholic fatty liver disease 6.
Clinical Significance
- Normal Alk Phos levels in patients with PBC are associated with better long-term outcomes, including a significant absolute complication-free survival gain at 10 years 2.
- Elevated GGT levels in patients with PBC may be a biomarker for disease activity and treatment response 3.
- Ursodeoxycholic acid (UDCA) treatment has been shown to decrease Alk Phos and GGT levels in patients with PBC and other liver diseases 4, 5.
Diagnostic Evaluation
- The evaluation of abnormal liver chemistries, including Alk Phos and GGT, should include a thorough medical history, physical examination, and laboratory testing, including viral hepatitis panels, autoimmune hepatitis panels, and imaging studies 6.
- A liver biopsy may be considered when serologic testing and imaging fail to elucidate a diagnosis, to stage a condition, or when multiple diagnoses are possible 6.