Considering the deficits in the nigrostriatal dopaminergic system in GDX rats in the present study and lower testosterone levels in some PD [65, 66] as well as the complex I deficiency in the pathogenesis of PD [16, 18–21], testosterone regulation of both ND1 and ND4 seemed related to the pathogenesis of PD with testosterone deficiency. Here, MT-ND4 is linked to Parkinson disease.