GPT and metabolic dysfunction-associated steatohepatitis: In 2000, the first uncontrolled study by Glubahar et al. showed a significant reduction in serum ALT, AST, and gamma-glutamyl transferase (GGT) levels by 3 months of NAC (1 g per day) treatment compared to those of baseline in 11 NASH patients (Gulbahar et al., 2000).