BACKGROUND AND OBJECTIVES: Abnormal thyroid function influences the cardiovascular system. In particular, brief thyroid functional change due to levothyroxine (LT4) suppression therapy and withdrawal in papillary thyroid cancer (PTC) patients can affect cardiovascular system and other biochemical markers. However, the effect of brief thyroid functional change on arterial stiffness has not been evaluated. Therefore, we evaluated the changes in arterial stiffness according to short-term thyroid hormone levels in patients who underwent total thyroidectomy and radioactive iodine (RAI) therapy for PTC. MATERIALS AND METHODS: Patients with PTC (n=17; 15 females, mean age 52 years) who underwent total thyroidectomy and RAI therapy were enrolled in this study. The arterial stiffness was evaluated using the corrected augmentation index for heart rate (AI@75) and brachial-ankle pulse wave velocity (BaPWV). Serum thyroid hormone levels and arterial stiffness parameters were checked three times consecutively: the day before thyroidectomy (Visit 1; baseline euthyroid state), after LT4 withdrawal (Visit 2; pre-RAI hypothyroid state) and 4 weeks after RAI (Visit 3; post-RAI thyrotoxic state). Biochemical markers, which can influence the arterial stiffness, were also measured. RESULTS: The heart rate, AI@75 and serum thyroid hormone levels changed significantly at each visit. BaPWV was not significantly changed. Changes in AI@75 correlated with systolic blood pressure (SBP), serum thyroid hormone levels, total cholesterol and high density lipoprotein cholesterol in univariate analysis. In multivariate analysis, SBP was the independent factor for AI@75 changes. CONCLUSION: These results suggest that brief thyroid functional changes can influence AI@75. And SBP was important factor for AI@75 change.