Similarly to the Glypican-4/Fat Body Mass (%) ratio, comparative analysis of ROC curves revealed that the AUC value for the Irisin/Fat Body Mass (%) ratio as a predictor for metabolic syndrome is statistically significantly different from analogous parameters for the following ratios: Irisin/Body Mass, Irisin/BMI, Irisin/Fat-Free Body Mass (%), Irisin/WHR, Irisin/WHtR, and Irisin/BAI (Table 7, Figure 3). This evidence concerns the gene FNDC5 and metabolic syndrome.