Gamma Glutamyl Transferase: Comprehensive Review

Background

Whitfield JB. Crit Rev Clin Lab Sci. 2001;38(4):263-355. PMID: 11563810

This comprehensive 93-page review represents the definitive clinical laboratory science reference on gamma-glutamyltransferase (GGT), covering biochemistry, clinical utility, and interpretation.

Study Design

Parameter	Details
Type	Comprehensive scientific review
Scope	GGT biochemistry, physiology, clinical applications
Coverage	>500 referenced studies
Author	Leading Australian clinical biochemistry researcher

Key Findings

Application	Clinical Utility
Hepatobiliary disease	Most sensitive liver enzyme for cholestasis
Alcohol monitoring	Elevated in 50-70% of heavy drinkers
Oxidative stress	Reflects glutathione metabolism status
Metabolic syndrome	Early marker preceding diabetes diagnosis
Cardiovascular risk	Independent predictor of CVD mortality

Reference ranges: Men <50 U/L, Women <32 U/L (though optimal likely lower).

Mechanistic Insights

GGT functions in glutathione recycling at cell membranes, making it a marker of oxidative stress. Elevated levels indicate increased antioxidant demand. The review details how GGT participates in amino acid transport and leukotriene metabolism.

Clinical Implications

Whitfield established that GGT elevation—even within "normal" range—is clinically significant and warrants investigation. The review shifted understanding of GGT from a simple alcohol marker to a multifaceted metabolic indicator.

Metabolic Health Perspective

This foundational review supports using GGT as part of comprehensive metabolic assessment. The GGT evaluator optimal threshold (<15-20 U/L) reflects levels associated with lowest disease risk rather than population-based reference ranges.