IGF2 and obesity due to melanocortin 4 receptor deficiency: In the clinic, FTO-associated overgrowth is reminiscent of the Beckwith-Wiedemann syndrome (BWS), which leads to overgrowth and IR, which also implicates both IGF2 and H19, and which is imperfectly modeled by any single mouse model64: BWS is a human genomic imprinting disorder at a locus harboring IGF2 and H19, that is characterized by overgrowth and early onset obesity65, although BWS is often an underestimated cause of syndromic obesity.