FGF21 and obesity due to melanocortin 4 receptor deficiency: Grade II obesity patients had the highest circulating concentrations of FGF21 (729.6 ± 200.9 pg/mL) and RBM3 (408.8 ± 133.9 pg/mL), while patients with a BMI of <25 presented with the lowest values (FGF21 = 311.7 ± 192.9 pg/mL; RBM3 = 285.5 ± 122.2 pg/mL) (Figure 3c,d).