Thyroid eye disease (TED) is an autoimmune disease, most commonly occurring in association with Graves’ hyperthyroidism although it can rarely occur in people with autoimmune hypothyroidism or normal thyroid function. There is a link between thyroid function abnormalities and poorer outcome of TED, therefore the restoration and maintenance of optimal thyroid function is essential in the management of TED. Different treatment modalities for hyperthyroidism have variable impact on the natural history of TED, with radioiodine treatment increasing the risk of new onset or worsening of TED. The risk is particularly high in patients with risk factors such as smoking, short duration of Graves’ hyperthyroidism, severe hyperthyroidism, untreated post-radioiodine hypothyroidism and pre-existing TED. A careful selection of patients, counselling the patients about the risk and symptoms of TED, providing smoking cessation advice and support, and the use of concomitant prophylactic steroid if indicated will reduce the risk of TED following radioiodine.