This is a retrospective cohort study aiming to investigate the associations of potential risk factors with thyroid dysfunction, and the relationship of thyroid dysfunction with adverse health outcomes. If any significant association is identified, we also aim to reveal the mediators that play a role in the association. Based on the variety of data available from UK Biobank, we expect to conduct a well-designed large cohort study to achieve the aforementioned aims. This project will approximately last for 3 years. We anticipate that the results would provide evidence for better prevention of thyroid dysfunction, and development of management strategy among individuals with thyroid dysfunction to reduce the occurrence of adverse health outcomes.