NPPA and intestinal obstruction: Elevated levels of 5-HT and other substances (neurokinin A, activin A, substance P, atrial natriuretic peptide, N-terminal pro-brain natriuretic peptide, chromogranin A (CgA), and connective tissue growth factor (CTGF)) are also implicated in the pathogenesis of fibrotic complications in the mesentery as well as in cardiac valves [21,22,23,24,25], the former leading to possible intestinal obstruction, the latter to CHD.