Thyrotoxicosis is a common endocrine disorder with an incidence of 0.2%, and when untreated, leads to congestive heart failure, arrhythmias and premature death. Maori appear both over-represented in the number of patients presenting with thyrotoxicosis and to have more severe disease. Definitive treatments for thyrotoxicosis are either radioactive iodine (I131) or surgical removal of the thyroid gland. Traditionally in Aotearoa/New Zealand, the preferred treatment option has been I131. We have recently identified that a single dose of I131 was less likely to achieve cure for Maori, when compared to non-Maori. The reasons for this disparity are unknown. Ethnic differences in presentation, severity and response to treatment of Maori compared with non- Maori patients presenting with thyrotoxicosis will be investigated prospectively in my doctoral thesis. The aim of this work is to identify differences in thyrotoxicosis and its treatment, and identify inequities based on ethnicity in order to optimise treatment for Maori.