FGF21 and obesity due to melanocortin 4 receptor deficiency: Out of the hormones studied in this paper, those which are typically upregulated in obesity include leptin [12,13], visfatin [14,15], apelin [16] and FGF21 (fibroblast growth factor 21) [17] (although, in case of the last two, there are conflicting data regarding childhood adiposity [16,18,19,20,21,22]), whereas adiponectin [23,24,25], ghrelin [13,26] and, probably, GLP-1 (glucagon-like peptide-1) [27] are usually downregulated.