Arathimos R, et al. - Researchers assessed genetic and observational evidence regarding the involvement of sex hormones in asthma. From a subset of 512 males in the Avon Longitudinal Study of Parents and Children, longitudinal data on sex hormone-binding globulin (SHBG), total and bioavailable testosterone and asthma were extracted to combine observational evidence and genetic evidence of SHBG and asthma using two-sample Mendelian randomisation (MR), a method of causal inference. Across two large data sets, the Trans-National Asthma Genetics Consortium genome-wide association study of asthma and UK Biobank (over 460 000 individuals combined), they meta-analysed two-sample MR findings. For the first time, suggestive evidence of a protective impact of genetically elevated SHBG on asthma was generated in this study.