“…At the onset of diabetes in this patient, his CPI was 0.7 and his ΔC-peptide on the glucagon loading test was 0.4 ng/ mL. The efficacy of GLP-1RA monotherapy or sulfonylurea combination depends on the remaining β-cell function (14). A ΔC-peptide on the glucagon loading test of 2.34 ng/mL or CPI of 1.86 have been reported as cut-off values for a longer therapeutic durability of initial GLP-1 RA in Japa-nese populations (15), suggesting that this particular case already possessed a reduced insulin secretory capacity at the initiation of GLP-1RA.…”