After adjusting for birth year and obesity, no association was found between PCOS and MS (HR = 0.91, 95% CI = 0.72–1.15), which was confirmed by Mendelian randomization analysis, where genetically predicted PCOS propensity, sex hormone-binding globulin (SHBG), or testosterone levels did not causally affect MS risk (all p-values > 0.05). Here, SHBG is linked to polycystic ovary syndrome.