Given uncertainty surrounding the role of various previously reported adipokines and CRP in breast cancer aetiology, we performed two‐sample MR analyses to evaluate the causal relevance of circulating adiponectin, HGF, IL‐6, leptin receptor, PAI‐1, resistin and CRP in overall and oestrogen receptor‐stratified breast cancer risk. The gene discussed is SERPINE1; the disease is breast cancer.