Previous MR studies have established associations between cathepsins and cancer risk, though not specifically with muscle-related outcomes.[23] For instance, elevated cathepsin H levels have been causally linked to an increased risk of lung cancer, particularly adenocarcinoma, in smokers, suggesting its potential as a biomarker for diagnosis and treatment.[24] Our MR analysis revealed that cathepsins S and E were positively associated with ALM, whereas cathepsins F and B were negatively associated with ALM. This evidence concerns the gene CTSS and lung cancer.