INS and pancreatic insulinoma: In our study, we found decreased insulin (before surgery, 30.47 ± 4.93 mU/L; after surgery, 6.28 ± 1.35 mU/L), proinsulin (before surgery, 77.74 ± 24.61 pmol/L; after surgery, 23.73 ± 6.60 pmol/L) and C-peptide levels (before surgery, 4.46 ± 0.62 ng/mL; after surgery, 2.22 ± 0.18 ng/mL) after surgery in all patients with insulinoma.