IGF1 and obesity due to melanocortin 4 receptor deficiency: This is consistent with the finding that diabetes and obesity mainly raise the risk for those cancers that exhibit a Warburg phenotype.43 The relevance of this pathway for tumorigenesis is demonstrated by the fact that humans with the Laron syndrome, a recessively inherited defect in the growth hormone receptor, display extremely low IGF-1 and reduced insulin concentrations and usually do not develop cancer despite high prevalence of obesity and dyslipidemia.44, 45