HTR5A and celiac disease: For example, 5-HT has been reported to increase the rate at which enterocyte precursors proliferate, and the enhancement of enterocyte proliferation by 5-HT might be mediated by a 5-HT2 receptor.53 Patients with celiac disease have increased 5-HT-containing enterochromaffin cell numbers and significantly higher peak plasma 5-HT and platelet 5-HT stores than controls, which correlate with postprandial dyspepsia.54 On the other hand, the biological activities of 5-HTP itself have not been essentially explored in the gut.