Moreover, as circulating post-prandial ghrelin is significantly reduced in PD patients [23] and cerebrospinal fluid levels of IL-6 are increased in both juvenile and adult onset PD [24,25], we speculate that a reduction in circulating ghrelin may exacerbate dopaminergic cell loss in human PD due to elevated IL-6 acting as a primer for neurodegeneration. This evidence concerns the gene GHRL and Adult onset.