INS and Insulin resistance: We considered all original studies in English language published from 1970 to January 2018 which reported as the primary or secondary objective of the study at least one of the following metabolic parameters: fasting glucose, fasting insulin, glycosylated hemoglobin (HbA1c), homeostatic model assessment of insulin resistance (Homa-IR), the quantitative insulin sensitivity check index (QUICKI), the insulin sensitivity index (ISI), or the M-value (derived from euglycemic hyperinsulinemic clamp).