TH and Parkinson disease: Furthermore, TH level in PD mice treated with ZnO NP showed a non-significant decrease by 0.15-fold (p-value 0.1103), a significant decrease with CoFe2O4 NP, and the dual NP administration by 0.311-fold (p-value 0.0004) and 0.42 (p-value 0.0003) respectively compared to PD mice, as shown in Figure 2.