INS and obesity due to melanocortin 4 receptor deficiency: Obesity is a risk factor for the development of postmenopausal breast cancer,6,7 and there is evidence that obesity is associated with poorer breast cancer survival.8–11 Obesity disproportionately affects African-Americans and Native Hawaiians compared to other racial/ethnic groups in the United States.12–14 There is additional evidence that insulin resistance is associated with poor breast cancer outcome.15 Mechanisms related to obesity and subsequent aberrations in insulin signaling may contribute to the differences in breast cancer outcomes across racial/ethnic populations.