IGF1 and obesity due to melanocortin 4 receptor deficiency: Consistent with this possibility, rodent studies have shown that IGF-1 overexpression in beta cells increases beta cell mass through neogenesis and replication.23 Insulin-like growth factor-1 may also enhance insulin action based on homology to insulin and binding to the insulin receptor,24 and administration of recombinant human IGF-1 in adults with obesity improves glycemia and insulin sensitivity.25,26 Whether modulating the IGF-1 pathway in youths with T2D may be beneficial remains an important question with implications for future therapies.