To this end, we studied the correlation of the levels of GDNF and HVA in the peripheral blood serum of PD patients with EF and its components (working memory, cognitive flexibility, and inhibitory control), in order to explore the possible mechanism of GDNF participating in the occurrence and development of EDF, and to provide a theoretical basis for early identification of cognitive dysfunction in PD. Here, GDNF is linked to Parkinson disease.