GDNF and Parkinson disease: The analysis shows that the Cons-PD group had higher mean GDNF levels (528.44 pg/ml) than the Cons-pro-PD group (360.72 pg/ml p = 0.000) and the Cons-Clinic-PD group (331.36 pg/ml p = 0.000), with no statistically relevant discrepancies found between the Cons-Pro-PD and Cons-clinic-PD groups (p > 0.05) (Figure 5B).