Epidemiological studies have shown that serum C-peptide, as a proxy measure of insulin release, is associated with increased risk of cancer of the colorectum, post-menopausal breast, pancreas and endometrium [108] and that type 2 diabetes is associated, independent of obesity, with breast, pancreas, kidney, endometrial, colorectal and bladder cancer [109]. Here, INS is linked to obesity due to melanocortin 4 receptor deficiency.