An inverse-variance weighted MR showed a one unit increase in circulating MSP concentrations (ng/ml) is associated with a 4% reduction in prostate cancer risk (OR = 0.96, 95% CI 0.95–0.97) (Table 4), and was not altered after adjustment for PSA (supplementary Table S8, available at Annals of Oncology online). The gene discussed is KLK3; the disease is Familial prostate cancer.