Hashimoto's Thyroiditis, Risk of Coronary Heart Disease, and L-Thyroxine Treatment: A Nationwide Cohort Study

Objective: Our objective was to investigate the risk of coronary heart disease (CHD) in patients with Hashimoto's thyroiditis (HT). Methods: The Taiwan National Health Insurance Research Database was used to conduct a retrospective cohort analysis. The cohort study consisted of 1165 newly diagnosed HT patients and 4660 matched controls (non-HT patients) from 2000 to 2010. The median follow-up time was 5.46 years. The risk of developing CHD for HT patients was measured using the Cox proportional hazards model. Results: The risk of developing CHD in HT patients was increased compared with the non-HT controls, with an adjusted hazard ratio (HR) of 1.44 (95% confidence interval [CI] = 1.05-1.99). The risk was significant in women but not in men, and restricted to subjects younger than 49 years. HT remained an independent risk factor after adjusting for comorbidities; however, combining with hypertension or hyperlipidemia further increased the risk of CHD (adjusted HR = 2.06, 95% CI = 1.46-2.92; and adjusted HR = 1.83, 95% CI = 1.31-2.55, respectively). Furthermore, HT without T-4 treatment and HT with treatment for less than 1 year were associated with higher risk of CHD (adjusted HR = 1.55,95% CI = 0.98-2.46; and adjusted HR = 2.42,95% CI = 1.43-3.97, respectively). The risk of CHD decreased after treatment with T4 for more than 1 year and did not differ from the non-HT cohort (adjusted HR = 0.84, 95% CI = 0.0.47-1.52). Conclusion: Patients with HT, are at higher risk of developing CHD compared with the general population. Treatment with T4 reduces the risk of CHD.