Considering the metabolic derangement commonly associated with obesity as well as the frequent use of metformin in overweight patients owing to its insulin-sensitizing effect and potential reduction of body weight [21], we aimed at assessing the impact of the metabolic phenotype, metformin-treated diabetes mellitus, and incident diabetes mellitus on thyroid function in euthyroid obese patients, and thus further investigating the potential thyroidal determinants of cardiometabolic risk in this setting. This evidence concerns the gene INS and diabetes mellitus.