Since a large and diverse list of hormones, adipokines and lipid mediators are implicated in promoting obesity-associated mammary tumorigenesis, our review will focus on a critical subset that work in concert to promote estrogen production (via aromatase activation) and tumorigenesis, specifically eicosanoids, inflammatory cytokines, leptin and adiponectin; however, we recognize that other mediators play a role in this process such as insulin, insulin-like growth factors, resistin nampt/visfatin and cholesterol as reviewed elsewhere [124,125,126]. The gene discussed is CYP19A1; the disease is obesity due to melanocortin 4 receptor deficiency.