Efficacy of selenium supplementation for mild-to-moderate Graves’ ophthalmopathy in a selenium-sufficient area (SeGOSS trial): study protocol for a phase III, multicenter, open-label, randomized, controlled intervention trial

BACKGROUND: The therapeutic effect of selenium has been demonstrated in mild Graves’ ophthalmopathy (GO) in a European region where selenium status is suboptimal. However, there is a lack of evidence to support selenium use in selenium-sufficient areas. The aim of this study is to evaluate the therapeutic effect of selenium in mild-to-moderate GO in selenium-sufficient South Korea. METHODS: The SeGOSS trial is a multicenter, prospective, randomized, open-label trial in South Korea. Eighty-four patients aged 19 years or older with mild-to-moderate GO will be randomized to receive either vitamin B complex alone or vitamin B complex with selenium for 6 months with three monthly follow-up visits. The primary outcome is comparison of the improvement in quality of life at 6 months from baseline between the control and selenium groups. The secondary outcomes are intergroup differences in changes in quality of life at 3 months, clinical activity of GO at 3 and 6 months, thyroid autoantibody titers at 3 and 6 months, and the response rate at 3 and 6 months from baseline. Quality of life will be measured by questionnaire for patients with GO, and the clinical activity of GO will be evaluated by the clinical activity score (CAS). A positive response is defined as either changes in the CAS < 0 or the changes in the GO-QOL score ≥ 6. DISCUSSION: The SeGOSS study will evaluate the therapeutic potential of selenium for mild-to-moderate GO in a selenium-sufficient area and provide support in tailoring better treatment for GO. TRIAL REGISTRATION: KCT0004040. Retrospectively registered on 5 June 2019. https://cris.nih.go.kr/cris/search/detailSearch.do/14160. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13063-023-07282-4.