INS and Hypoinsulinemia: The concentration of plasma insulin was herein quantified as a marker of the functional capacity of pancreatic β cells, finding a significant difference between the tacrolimus and control groups at week 4 (0.404 ng/mL vs 1.55 ng/mL, respectively), indicating hypoinsulinemia in the experimental animals.18 The same condition is also shown in 12-week-old GK rats, reported to have an average concentration of ~1.25 ng/mL of insulin.46