Orexin A/Hypocretin-1: ProductsOrexin A and orexin B are neuropeptide hormones derived from proteolytic processing of the same orexin precursor protein. Orexins are named for their orexigenic-inducing (orexis; Greek for appetite) activity. They are released from the hypothalamus and are involved in the regulation of sleeping patterns, feeding, and metabolism. Orexins A and B are less than 50% amino acid identical. Orexin A is a ligand for two 7-transmembrane orexin receptors, OX1R and OX2R, while orexin B preferentially binds OX2R. Defects in the orexin precursor are a cause of narcolepsy in humans.