In addition to affecting lipid metabolism, obesity can affect the risk of gallstones and gall bladder cancer through adverse changes in the metabolism of endogenous hormones, including sex steroids, sex hormone-binding globulin, insulin growth factor-I, and inflammatory mediators, such as insulin and cytokines; all of these stimulate cell proliferation and inhibit apoptosis, thereby enhancing the potential for tumour growth (Coussens and Werb, 2002). The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.