FGF21 and obesity due to melanocortin 4 receptor deficiency: In this study, serum FGF-21 levels in the FP group were significantly higher than those in healthy controls, which is consistent with the previously reported changes in serum FGF-21 levels observed in other metabolic diseases, such as fatty liver, obesity, and diabetes (Li et al., 2018; Akour et al., 2017; Li et al., 2010; Keuper, Häring & Staiger, 2019).