IL6 and obesity due to melanocortin 4 receptor deficiency: Over the past decade, interleukin-6 (IL-6) has emerged as a highly versatile cytokine with important repercussions for the endocrine system, particularly in obesity and insulin resistance (Bastard et al., 2000; Nieto-Vazquez et al., 2008; Senn et al., 2002; Wallenius et al., 2002).