GDF15 and inborn mitochondrial metabolism disorder: GDF15 is also involved in mitochondrial diseases (Kalko et al., 2014; Montero et al., 2016; Yatsuga et al., 2015) and all‐cause mortality (Wiklund et al., 2010), regulates appetite, weight loss, and cancer‐related anorexia (Breit et al., 2011; Johnen et al., 2007; Lerner et al., 2015; Tsai, Lin, Brown, Salis, & Breit, 2016; Tsai et al., 2013, 2014; Villars, Pietra, Giuliano, Lutz, & Riediger, 2017).