Many gastrointestinal hormones have been associated with PPH, including insulin, GLP-1, GLP-2, glucose-dependent insulinotropic polypeptide (GIP), somatostatin, calcitonin gene-related peptide (CGRP), neurotensin, and vasoactive intestinal peptide (VIP) [12,21]. The gene discussed is GCG; the disease is pulmonary arterial hypertension.