Influence of short-term selenium supplementation on the natural course of Hashimoto's thyroiditis: clinical results of a blinded placebo-controlled randomized prospective trial.

Abstract

The real efficacy of selenium supplementation in Hashimoto's thyroiditis (HT) is still an unresolved issue. We studied the short-term effect of L-selenomethionine on the thyroid function in euthyroid patients with HT. Our primary outcome measures were TSH, thyroid hormones, thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb) levels and thyroid echogenicity after 6months of L-selenomethionine treatment. The secondary outcome measure was serum CXCL10 levels. In a placebo-controlled randomized prospective study, we have enrolled untreated euthyroid patients with HT. Seventy-six patients were randomly assigned to receive L-selenomethionine 166µg/die (SE n=38) or placebo (controls n=38) for 6months. TSH, free T4 (FT4), free T3 (FT3), TPOAb and CXCL10 serum levels were assayed at time 0, after 3 and 6months. An ultrasound examination of the left and right thyroid lobe in transverse and longitudinal sections was performed. A rectangular region, the region of interest, was selected for analysis. TSH, FT4, FT3, TPOAb, thyroid echogenicity and CXCL10 were not statistically different between SE and control groups at time 0, after 3 and 6months. In the SE group, FT4 levels were significantly decreased (P<0.03) after 3months, while FT3 increased (P<0.04) after 3 and 6months versus baseline values. In the control group, the FT3 decreased after 3 and 6months (P<0.02) compared to baseline. The short-term L-selenomethionine supplementation has a limited impact on the natural course in euthyroid HT. Our results tip the balance toward the ineffectiveness of short-term L-selenomethionine supplementation in HT.