IR was found in 26.4%, and upon multivariate analysis, it was substantially related to older age, obesity, larger tumor size, advanced stage, and high proliferative luminal B/HER2-negative subtype in postmenopausal women. In premenopausal women, however, only obesity was associated with IR. This evidence concerns the gene ERBB2 and obesity due to melanocortin 4 receptor deficiency.