Recent advances in the phylogenetic study of ghrelin

► Ghrelin is a multifunctional hormone with more features than we have originally postulated. ► To understand what is ghrelin, it is also important to know the evolutional process. ► Ghrelin is present in non-mammalian vertebrates and plays crucial roles. ► Comparative study between mammalian and non-mammalian vertebrates let us know the generality and difference. ► In this review, we summarized recent literatures on the ghrelin system of non-mammalian vertebrates.