Therefore, based on a cohort of FDRs, we employed the highly sensitive and specific methods for testing specific insulin and proinsulin and aimed to explore the relative roles of IR and β-cell dysfunction in the early stage of T2DM development in Chinese population and examine the usefulness of proinsulin and proinsulin-to-specific insulin ratio in detecting alterations of β-cell function. This evidence concerns the gene INS and type 2 diabetes mellitus.