GDF15 and inborn mitochondrial metabolism disorder: GDF15 levels are high in animal models with mitochondrial dysfunction, patients affected by mitochondrial disease, and in older than in younger persons, possibly as a response to impaired calcium homeostasis and excessive oxidative stress (Davis, Liang, & Sue, 2016; Fujita, Taniguchi, Shinkai, Tanaka, & Ito, 2016).