Elevated Serum Ghrelin Exerts an Orexigenic Effect that May Maintain Body Mass Index in Patients with Metastatic Neuroendocrine Tumors
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- Wang, H.S., Oh, D.S., Ohning, G.V. et al. J Mol Neurosci (2007) 33: 225. doi:10.1007/s12031-007-0004-9
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Ghrelin is a potent orexigenic peptide principally produced in the stomach by a distinct population of neuroendocrine cells in the oxyntic mucosa of the fundus. Exogenous ghrelin given as an intravenous infusion has been shown to increase caloric intake in patients with cancer cachexia. In this study, we hypothesized that elevated endogenous ghrelin, produced by increased neuroendocrine cell tumor burden, also exerts an orexigenic effect helping to maintain body mass index. To evaluate the effect of elevated endogenous ghrelin, 35 patients with neuroendocrine tumors were enrolled, assigning them to one of two groups depending on the presence of hepatic metastases. Following an overnight fast, serum was collected and sent for ghrelin measurement by an outside laboratory. The two groups were well matched for all other relevant clinical variables including subtype of tumor, primary location of tumor and tumor treatment history. Nearly all patients with hepatic metastases had elevated levels of ghrelin compared to the standard reference range given for matched controls. The presence of hepatic metastases was associated with significantly elevated ghrelin levels (p<0.05) and a greater mean body mass index. In addition, we report a positive correlation between serum ghrelin and total tumor surface area and between serum ghrelin and body mass index, suggesting that elevated endogenous ghrelin may be sufficient to overcome any partial ghrelin resistance typically seen in cancer cachexia. These results support the possibility that ghrelin is co-released from neuroendocrine tumors and exerts an orexigenic effect in these patients, helping to maintain their body mass index despite widely disseminated disease.