DPP4 and type 2 diabetes mellitus: Noh et al. reported that using a DPP-4 inhibitor alone increases the metastasis of primary thyroid cancer with HR 3.89 (95%CI: 1.04–9.64) in T2DM patients, whereas a combination with metformin attenuated such an undesirable effect of DPP-4 inhibitor (HR 0.75, 95%CI: 0.57–1.01) [130].