While no relevant alterations in the blood levels of ghrelin have been observed in AD patients (Proto et al., 2006; Theodoropoulou et al., 2012), the basal plasma levels of ghrelin and the postprandial secretion of the hormone were diminished in PD patients (Fiszer et al., 2010; Unger et al., 2011). Here, GHRL is linked to Alzheimer disease.