Davis RL, et al. - One hundred twenty-one individuals with Parkinson disease (PD) and 103 age-matched healthy controls were enrolled from a single center in order to systematically evaluate serum fibroblast growth factor 21 (FGF-21) and growth differentiation factor 15 (GDF-15), together with mitochondrial DNA (mtDNA) copy number levels in peripheral blood cells from people with PD and healthy controls, to ascertain whether these measures could act as a biomarker of PD. When contrasting individuals with PD with healthy controls, no significant variations recognized for any of the measures were noted. This reflected a lack of diagnostic sensitivity that is inconsistent with these measures being utilized as biomarkers for PD. In conclusion, serum FGF-21, serum GDF-15, and blood mtDNA levels were comparable in individuals with PD and healthy controls and hence incredible to be competent indicators of mitochondrial dysfunction in people with PD.