Summary

Thyroid dysfunction and diabetes mellitus frequently occur together, with evidence showing higher rates of each condition in individuals affected by the other. Beyond their statistical association, emerging research indicates shared mechanisms involving autoimmunity, obesity, ageing and insulin resistance, which might explain their bidirectional relationship. This Review synthesizes current evidence on these links, with a particular focus on how thyroid dysfunction influences glycaemic control and how antidiabetic therapies affect thyroid function. Unlike earlier reviews, we frame thyroid disorders within the broader category of non-communicable diseases (NCDs), emphasizing their public health relevance and the need for greater attention in global funding and policy agendas. By combining clinical insights with a population health perspective, this Review aims to promote earlier detection, integrated management strategies and recognition of thyroid disease as a neglected NCD priority.