Technical Abstract: Apart from MC3R another four melanocortin receptors (MC1R, MC2R, MC4R and MC5R) that mediate diverse biological effects of pro-opiomelanocortin (POMC) derived peptides have been described. MC1R, MC2R, and MC5R have established roles in pigmentation in the skin, adrenal steroidogenesis and thermoregulation, respectively, while MC4R is involved in control of feeding behaviour and MC3R has an important role in energy homeostasis. MC3R knockout mice are obese, but in contrast to MC4R-deficient mice, these animals are not hyperphagic. It suggests that MC3R mediates a regulatory feedback mechanism in the hypothalamus. However, the precise role of MC3R remains ill-defined. Associations between polymorphism in MC3R gene and obesity have been detected in humans. The porcine MC3R maps to a chromosome region harbouring QTL for fat traits in the German Meishan x Piétrain pedigree.