There is marked variability in the upper limit of normal (ULN) for ALT in clinical practice guidelines published by the European Association for Study of the Liver (the traditional 40 U/L) (12, 13), and the American Association for the Study of Liver Diseases (AASLD) (35 U/L for males and 25U/L for females) (14). The gene discussed is GPT; the disease is liver disorder.