GPT and Parkinson disease: On the basis of ALT being protective in both sexes we investigated the common clinical indicator of liver disease, the AST:ALT ratio which was significantly elevated at both -10 to -5 years (1.20 +/- 0.40, P<0.05) and -5 to 0 years before diagnosis (1.29 +/- 0.41, P<0.001) and 0–5 years after diagnosis in males (1.39 +/- 0.55, P<0.001) compared to non-PD (1.17 +/- 0.39, Fig 5C).