Supplementary Material for: A 2018 European Thyroid Association Survey on the Use of Selenium Supplementation in Hashimoto’s Thyroiditis

Objective: To investigate clinical practice regarding the use of selenium supplementation in patients with Hashimoto’s thyroiditis (HT) among members of the European Thyroid Association (ETA). Methods: ETA members were invited to participate in an online survey investigating the use of selenium supplementation across the spectrum of benign thyroid diseases. Of 872 invited members, 242 (28%) completed the survey. After exclusion of basic scientists and non-European members, survey data from 212 respondents were eligible for further analyses. Responses from 65 (31%) individuals who did not at all recommend selenium, or only considered its use in the setting of a clinical trial, were not included in the final analysis of survey data from 147 respondents. ­Results: While only a minority of respondents (29 of 147, 20%) stated that the available evidence warrants the use of Se in patients with HT, a statistically significant majority (95 of 147; 65%, p < 0.001) used Se occasionally or routinely. Se was predominantly recommended for patients with HT not receiving LT4 (102 of 147; 69%) to reduce circulating thyroid autoantibody levels. Very few respondents routinely recommended Se to pregnant patients with HT. Conclusions: A minority of responding ETA members stated that the available evidence warrants the use of Se in HT, but a majority recommended it to some extent, especially to patients not yet receiving LT4. This is questionable, and selenium is not recommended to patients with HT according to current ETA guidelines. Ongoing and future trials may lead to the reversal of current medical practice.