ESR1 and obesity due to melanocortin 4 receptor deficiency: Premenopausal women with obesity are at an increased risk for triple-negative breast cancer, which lacks the expression of estrogen receptor (ER), progesterone receptor, and human epidermal growth factor receptor 2 [9,10,11], while postmenopausal women with obesity have an increased risk for ER+ breast cancer [12,13].