GCH1 and Alzheimer disease: The specific mechanisms are as follows: (1) a GPX4-mediated ferroptosis defense system can alleviate lipid peroxidation and protect DA neurons; (2) an FSP1-mediated ferroptosis defense system can effectively inhibit ferroptosis, thus inhibiting the production of lipid peroxidation and exerting its neuroprotective effect; (3) GCH1 mutation can affect the PD phenotype, and its defense system can play a neuroprotective role; and (4) GPX4-, FSP1-, and GCH1-mediated ferroptosis defense systems can effectively inhibit AD ferroptosis and play a neuroprotective role.