In addition, FGF21, coding for fibroblast growth factor 21, an atypical member of FGF family active on glucose and lipid metabolism [16] and on adiponectin production, was prominently upregulated in the liver of PTHrP-overexpressing mice, thereby resulting beneficial for the mitigation of the obesity-linked metabolic diseases such as hepatic steatosis, insulin resistance, and glucose intolerance. This evidence concerns the gene FGF21 and obesity due to melanocortin 4 receptor deficiency.