Thyroid dysfunction following radioiodine for Graves' disease is common, potentially detrimental and avoidable. A variety of clinical strategies are employed in the post-radioiodine era util the patient is on a stable thyroid hormone replacement regimen, which include the use of anti-thyroid drugs, antithyroid drugs with thyroxine, early thyroxine replacement and watchful monitoring until the onset of hypothyroidism. Which of these is most effective in avoiding dysthyroidism, is unknown. This study aims to address this lack of evidence. It will focus on Graves' disease as this is the commonest cause of thyrotoxicosis and the commonest indication for RI therapy. It will provide an insight into potential strategies for improving important clinical outcomes.