FGF21 and obesity due to melanocortin 4 receptor deficiency: Our primary aim was to study the value of important metabolic regulators implicated in obesity and insulin resistance (fibroblast growth factor 21 [FGF21], leptin, adiponectin and insulin-like growth factor binding protein 1 [IGFBP1]) as markers of metabolic health in overweight/obese children and those with normal weight.