Selenium (Se) is an important element that exerts its effects through selenoproteins. The thyroid gland has the highest Se concentration and specific selenoprotein enzymes families are crucial in the thyroid hormone metabolism. There is little evidence on the link between Se and thyroid autoimmune disease, therefore future studies are required to elucidate the nature of this associ ation.
Aim: To evaluate the Se status in euthyroid subjects with autoimmune thyroiditis.
Material and methods: From January 2014 to January 2015 we recruited 100 consecutive euthyroid subjects with autoimmune thyroiditis, living in the same region and with normal iodine intake. Serum concentrations of Se, thyroid antibodies (antithyroperoxidase--TPOAb--and antithyroglobulin--TgAb), thyroid-stimulating hormone (TSH), and thyroid ultrasound were performed in all patients.
Results: Mean age of the study group was 48.87 ± 12.83 years, range: 18-82 years. Since thyroid pathology is more frequent in the 5th - 6th decades of life we selected the age of 50 for the comparative analysis of the results (51% of patients were under 50). No statistical age-group differences in antibody levels were found: mean TPOAb = 420.95 IU/ml, p = 0.840; mean TgAb = 327.98 IU/ml, p = 0.977. TSH mean was 2.14 [μIU/ml, with no significant age-group differences (p = 0.176). Se levels ranged between 8.05 - 998.50 μg/ with a mean value of 294.96 μg/L and no significant differences between age groups (p = 0.158). Thyroid ultrasound showed inhomogeneity in 89%, nodules in 35% of patients, and a mean thyroid volume of 11.72ml, with no significant age-group differences (p = 0.366). The low TSH levels were associated with low Se levels in 11.6% of cases, but the direct correlation was statistically insignificant (r = 0.116; R2 = 0.0161; p = 0.371). Depend ing on TSH percentiles, mean Selevels showed no significant differences, however pointing out the highest mean value at the 25th percentile (F = 0.441, df = 61, p = 0.646). A negative correlation trend was found between Se and TPOAb (r = -0.2276) or TgAb (r = -0.2190) but lacking statistical significance (p=0.099).
Conclusion: Our results showed a weak negative correlation between Se and antithyroid antibodies, suggesting that selenium supplementation may improve the course of thyroid autoimmunity.