TGFB1 and hepatocellular carcinoma: Per unit increase in circulating TGF-β1 was significantly and causally associated with a 38% (OR, 95 CI: 1.38, 1.03–4.65) and 49% (OR, 95 CI: 1.49, 1.01–6.06) increased risk of having hepatocellular carcinoma under homozygous-genotype and dominant models, respectively.