Gamma-Glutamyl Transferase (GGT)
Gamma-glutamyl transferase is a membrane-bound enzyme located on the canalicular surface of biliary epithelial cells and renal brush border membranes, participating in cellular glutathione recycling.
Standard vs. Optimal Reference RangesU/L
Standard reference intervals represent the statistical 95% distribution of unselected commercial populations. Optimal longevity targets reflect clinical evidence for lowest cardiometabolic and all-cause mortality risk.
Your value falls within the optimal target associated with lowest disease risk and longevity.
9 - 48 U/L
General reference distribution across unselected commercial populations.
10 - 20 U/L
Concentration target associated with minimal all-cause cardiometabolic mortality.
Molecular Mechanism & Clinical Purpose
GGT transfers the gamma-glutamyl moiety of extracellular glutathione to amino acids and peptides, initiating the breakdown and cellular re-uptake of cysteine for intracellular glutathione synthesis. Elevated GGT reflects oxidative stress and biliary ductal irritation.
Differential Diagnosis
Elevated Levels (GGT High)
- •Chronic alcohol consumption (sensitive induction)
- •Cholestasis and biliary obstruction (alongside Alkaline Phosphatase)
- •Non-alcoholic fatty liver disease (MASLD)
- •Medications (phenytoin, carbamazepine, barbiturates)
Low Levels (GGT Low)
- •Optimal biliary epithelial integrity and low oxidative burden
Technical Reference & Deep Dive
Biochemistry & Enzymatic Pathways
Longevity Risk Architecture & Epidemiology
Pre-Analytical Caveats & Diagnostic Workup
Pre-Analytical Considerations:
A 12-hour overnight fast is recommended, especially if assessing biliary markers or lipid-associated hepatic enzymes. Complete abstinence from ethanol for at least 48 to 72 hours prior to testing is mandatory to prevent enzyme induction. Avoid strenuous unaccustomed weightlifting for 48 hours prior, which can release muscular transaminases and elevate AST/ALT.
Reflexive Testing Protocol:
- Comprehensive Hepatic Viral Panel (Hepatitis A IgM, HBsAg, HBcAb, HCV antibody with reflex PCR)
- Vibration-Controlled Transient Elastography (FibroScan) or Magnetic Resonance Elastography to quantify hepatic fat and fibrosis
- Serum Ferritin and Total Iron-Binding Capacity (TIBC) to screen for hereditary hemochromatosis
- Autoimmune Liver Disease Serology (Anti-Nuclear Antibodies, Anti-Smooth Muscle Antibodies, Anti-Mitochondrial Antibodies)
- Abdominal Right Upper Quadrant Ultrasound to assess hepatic parenchyma, biliary ducts, and portal vein flow
Clinical Citations & Primary Literature (1)
- [1]Gamma-Glutamyltransferase as a Predictive Biomarker of Cardiovascular and All-Cause Mortality - Lancet Gastroenterology & Hepatology (2021). PMID: 33711298
Associated Longevity Guides & Clinical Calculators
Medicine 3.0Explore comprehensive evidence-based clinical protocols, testing costs, and algorithmic calculators that incorporate Gamma-Glutamyl Transferase (GGT) into overall healthspan optimization.