GCG and obesity due to melanocortin 4 receptor deficiency: The analysis of obesity and diabetes markers in serum samples (T0-T3) using Bio-Plex Pro Human Diabetes 10-Plex Assay, which allows for the simultaneous analysis of C-peptide, ghrelin, gastric inhibitory peptide (GIP), glucagon-like peptide 1 (GLP-1), glucagon, insulin, leptin, plasminogen activation inhibitor-1 (PAI-1), resistin and visfatin.