FNDC5 and Parkinson disease: Also in PD, mitochondrial defects and energy are the main causes of the onset of the disease (19), On the other hand, because Irisin regulates energy balance, so there may be a relationship between them.Since there has been no research on the association of PD with Irisin, in this study we evaluated whether Irisin can play an effective role in neurodegenerative disease.