GPT and irritable bowel syndrome: In their study, the upper limits normal values for serum liver enzymes were de­fined as 41 international per liter in males and 31 international units per liter in females for ALT. However, compared to subjects without IBS, those with IBS had significantly higher values for BMI, waist circumference (WC), ALT, alkaline phosphate (ALP), γ-GT, total cholesterol (TC), triglyceride (TG), and low-density lipoprotein (LDL) cholesterol.