LEP and obesity due to melanocortin 4 receptor deficiency: Obesity, type 2 diabetes and the metabolic syndrome also have in common an increased production of leptin (Zhang et al. 1994; Kershaw et al. 2004) and a decreased production of adiponectin (Scherer PE et al. 1995; Hu E et al. 1996; Maeda K et al. 1996) by adipose tissue, with consequent elevations and reductions, respectively, in the circulating levels of these adipokines.