Subclinical hypothyroidism affects insulin secretion and impairs vascular function, increasing diabetic nephropathy and retinopathy risk, as well as peripheral arterial disease and neuropathy;12 excess circulating thyroid hormone in hyperthyroidism also associates with poor glycemic control and endothelial dysfunction, increasing cardiovascular complications.12 Among euthyroid subjects, fT4 close to the upper limit of normality associates to more frequent type 2 diabetes2 while TSH and type 2 diabetes do not show a clear linear relationship. This evidence concerns the gene INS and type 2 diabetes mellitus.