TCF7L2 and diabetes mellitus: First, most of the included studies were designed to study the association of TCF7L2 variants with diabetes [11, 13, 15–17, 19, 20, 26, 28, 29, 31], hyperglycemia [23, 25], and coronary artery disease [10] and only 2 studies [8, 9] were exclusively designed to examine the association between rs7903146 and plasma lipid levels.