The melanocortin family consists of five melanocortin G-Protein-coupled receptors (designated MC1-5R). The melanocortins, a-, ß- and ?-melanocyte-stimulating hormones (MSHs), are peptides derived from a precursor protein POMC, and play important roles in energy balance, reproductive function, pigmentation and inflammation. MC4 receptors with high affinities for a-MSH and ACTH are expressed almost exclusively in the CNS and appear to play a prominent role in energy homeostasis.