INS and thyroid cancer: Recent basic researches also suggested that metformin may sensitize thyroid cancer cells to oxidative stress [38], inhibit thyroid cancer stem cells [25], [39], cause cell cycle arrest at G0/G1 phase [25], induce apoptosis [25], inhibit colony formation [25], inhibit stimulation of mitogen-activated protein kinase by insulin [25], and inhibit growth of doxorubicin-resistant thyroid carcinoma cells [25].