RESUMEN
INTRODUCTION: The objective of this study was to evaluate the effect of selenium supplementation on autoantibody titres, thyroid ultrasonography, and thyroid function in patients with Hashimoto's thyroiditis (autoimmune thyroiditis) and normal thyroid reference range. MATERIAL AND METHODS: A total of 100 patients were given 200 ug/d selenium yeast orally, their thyroid function, levels of serum selenium, thyroid peroxidase antibodies (TPOAb), thyroglobulin antibodies (TGAb), and urine iodine were measured, and thyroid ultrasonography was performed before administration and three and six months afterwards, and the data were statistically analysed. RESULTS: The subjects exhibited a selenium deficiency before the administration of selenium, and the serum levels increased to moderate levels three and six months after the selenium supplementation (p < 0.05). The titres of TGAb decreased significantly in patients after six months of selenium supplementation (p < 0.05). In the high antibody group, TgAb decreased after 6 months compared with baseline (p = p < 0.05), and TPOAb decreased after 3 and 6 months of selenium supplementation compared with baseline (p < 0.05). CONCLUSION: In patients with autoimmune thyroiditis and normal thyroid reference range, there was a general selenium deficiency, but after six months of treatment it was shown that selenium supplementation may be effective in reducing the titres of TGAb and TPOAb.