Gamma-glutamyl transferase (GGT) is elevated in isolation in a 40-year-old asymptomatic male with no jaundice. Which of the following best explains this finding?

• A Obstructive jaundice causing bile reflux into sinusoids
• B Haemolysis releasing red cell GGT into circulation
• C Renal tubular disease causing urinary GGT spillage into blood
• D Enzyme induction by alcohol or drugs such as phenytoin increasing hepatic GGT synthesis ✓

Explanation

GGT is a highly inducible microsomal enzyme; chronic alcohol use and drugs that induce CYP450 (phenytoin, rifampicin, barbiturates) increase hepatic GGT transcription, leading to isolated GGT elevation even without cholestasis. Obstructive jaundice raises GGT but also raises ALP and bilirubin; it is not usually isolated. Red blood cells contain negligible GGT; haemolysis raises LDH, not GGT. GGT is a plasma membrane enzyme of tubular cells but is not released into blood in renal disease.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.