IFNγ-Inducible Chemokines Decrease Upon Selenomethionine Supplementation in Women with Euthyroid Autoimmune Thyroiditis: Comparison Between Two Doses of Selenomethionine (80 or 160 μg) Versus Placebo

Background: Several studies have suggested that selenium may influence the natural history of autoimmune thyroiditis (AIT). Recently, IFNγ-inducible chemokines (CXCL-9, -10 and -11) were shown to be elevated in AIT patients.

Objective: This prospective, randomized, controlled study was conducted to evaluate the effect of two doses of selenomethionine (Semet; 80 or 160 µg/day) versus placebo in euthyroid women with AIT, in terms of reduction of anti-thyroid antibodies, CXCL-9, -10 and -11 and improvement of thyroid echogenicity, over 12 months.

Patients And Methods: Sixty patients, aged 21-65 years, were equally randomized into 3 groups: placebo, 80 µg/day of Semet (80-Semet) or 160 µg/day of Semet (160-Semet).

Results: Anti-thyroperoxidase antibody (TPOAb) levels remained unaffected by Semet supplementation; anti-thyroglobulin antibody levels showed a significant reduction in the 160-Semet and the placebo group at 12 months. No significant change in thyroid echogenicity, thyroid volume and quality of life was observed within and between the groups. Subclinical hypothyroidism was diagnosed in 2 patients of the placebo group versus 1 patient in each Semet group. Serum CXCL-9 and -10 were significantly reduced in both Semet groups at 6 and 12 months, while they remained unchanged or increased in the placebo group. CXCL-11, TNFα and IFNγ showed a transient decrease at 6 months in both Semet groups but returned nearly to the basal levels at 12 months.

Conclusions: Semet supplementation had no positive effect on thyroid echogenicity or TPOAb in our patients. However, we observed a Semet-dependent downregulation of the IFNγ-inducible chemokines, especially CXCL-9 and -10, which may serve as helpful biomarkers in future selenium supplementation trials.