The results revealed that even after adjusting for other types of cathepsins, elevated cathepsin H levels retained a robust association with an increased risk of overall lung cancer (IVW: p = 1.460 × 10–4, OR = 1.070, 95% CI = 1.033–1.109) and adenocarcinoma risk (IVW: p = 8.854 × 10–5, OR = 1.094, 95% CI = 1.046–1.144) (Fig. 2). This evidence concerns the gene CTSS and lung cancer.