The Effect of Adding Selenium to Levothyroxine on Controlling Primary Overt Hypothyroidism and Serum Level Thyroid Peroxidase Antibody: A Double-blinded Randomized Clinical Trial

Introduction: This study examined the effect of adding selenium to levothyroxine on controlling  primary overt hypothyroidism and reducing the serum level of thyroid peroxidase antibody. Materials and Methods: This study was a double-blind, randomized clinical trial on individuals with primary autoimmune hypothyroidism. The patients were randomly divided into two intervention (I) and control (C) groups. Group I was treated with levothyroxine plus selenium, and Group C was treated with levothyroxine alone for three months. The anti-TPO antibody titer and serum levels of TSH, T3, and T4 were measured before and after treatment. Individuals were matched according to the season of visit and body mass index. Results: Fifty-three persons with a mean age of 33 years (10% male) participated in this study. Twenty-one individuals in Group I and twenty individuals in Group C completed the study. There was no significant difference between the two groups regarding age and gender. In none of the groups, anti-TPO antibody titer did not change significantly before and after the intervention. The serum level of the antibody did not differ significantly between the two groups before and after the study. Following the treatment, Group C was euthyroid; however, the intervention group, despite a decrease in TSH and an increase in T3 and T4, was not euthyroid. The participants reported no side effects. Conclusion: In this study, adding selenium to levothyroxine sodium did not significantly change the serum level of anti-TPO, TSH, T3, and T4 in the patients with overt primary hypothyroidism.