Coleman et al. also showed that obesity has been attributed as a risk factor for breast cancer development for over five decades and the contribution of obesity to postmenopausal breast cancer risk is thought to be related to elevated level of circulating estrogens in these women, resulting from aromatase-mediated conversion of androgens to estrogens in peripheral adipose tissue (and possible dysregulation of aromatase expression) and lower level of sex hormone-binding globin38. This evidence concerns the gene CYP19A1 and obesity due to melanocortin 4 receptor deficiency.