RETN and obesity due to melanocortin 4 receptor deficiency: Hormones produced by adipose tissue, referred to as adipokines, are secreted into the blood stream during physiological conditions, but weight gain and obesity pathologically change the gene expression and secretory pattern of such compounds, significantly elevating the levels of proinflammatory adipokines such as leptin, MCP-1, IL-6, and resistin while decreasing the production of anti-inflammatory adiponectin and IL-10.