Recently, among adipokines (i.e., cytokines associated with chronic inflammatory state and obesity) such as leptin, adiponectin, and resistin, only the serum level of resistin was found to be related strongly to the severity of pain in the patients undergoing laparotomy (Hozumi et al., 2018). This evidence concerns the gene RETN and obesity due to melanocortin 4 receptor deficiency.