IGF1 and obesity due to melanocortin 4 receptor deficiency: Furthermore, in addition to the effect on sex hormones, there are other biological effects of obesity, including insulin resistance, where levels of insulin and bioavailability of IGF are increased, which promotes cell division and inhibits apoptosis.17 Obesity also increases concentrations of adipokines (e.g., leptin) and proinflammatory cytokines (e.g., tumor necrosis factor‐α), which may contribute to cancer development.17, 18