Ghrelin is a 28-amino acid peptide mainly produced in the stomach and small intestines. Its receptor is the growth hormone secretagogue receptor (GHSR) 1a. Rhea et al. investigated whether ghrelin transport across the blood-brain barrier (BBB) is GHSR dependent by using a Ghsr null mouse model. They show for the first time that the GHSR is not solely responsible for ghrelin transport across the BBB.