However, in a landmark 2019 study of 1019 individuals with T1D for more than 50 years, who were prospectively followed for 4 years, Yu et al (19) reported that only 32% of the subjects had documented measurable SCP after using a combination of MMTT and hyperglycemic clamp with arginine infusion to estimate SCP; even though all 68 studied pancreases of their cohort were positive for insulin-containing β-cells. Here, INS is linked to type 1 diabetes mellitus.