RETN and type 2 diabetes mellitus: In obese patients with T2DM, ghrelin positively correlated with GIP (r = 0.305), insulin (r = 0.420), and resistin (r = 0.313) and negatively correlated with BMI (r = −0.318), glucagon (r = −0.426), and visfatin (r = −0.319) (p < 0.05) (Figure 3C).