CASR and gastrin-producing neuroendocrine tumor: This reduction in CASR mRNA was confirmed by quantitative PCR in the independent cohort of fresh frozen tissue from the Mayo Clinic, which revealed significantly reduced CASR expression in gastrinomas, insulinomas, and NF‐PNETs compared to that in normal islets (p < .00001, p < .0005, and p < .0001, respectively, Figure 1C).