In both sexes, circulating levels of free IGF1 [54], total IGF1, IGF2 [55,56,57] and IGFBP3 [58] are reported to be increased in humans and rodents with obesity, although some studies found no changes in total IGF1 in patients with obesity [54]. The gene discussed is IGF2; the disease is obesity due to melanocortin 4 receptor deficiency.