Context: Supplemental selenium (Se) may affect the clinical course of Graves disease (GD).
Objective: Evaluate efficacy of add-on Se on medical treatment in GD.
Design: Double-blind, placebo-controlled, randomized supplementation trial.
Setting: Academic endocrine outpatient clinic.
Patients: Seventy untreated hyperthyroid patients with GD.
Intervention: Additionally to methimazole (MMI), patients received for 24 weeks either sodium selenite 300 µg/d po or placebo. MMI was discontinued at 24 weeks in euthyroid patients.
Main outcome measures: Response rate (week 24), recurrence rate (week 36), and safety.
Results: A response was registered in 25 of 31 patients (80%) and in 27 of 33 (82%) at week 24 [odds ratio (OR) 0.93; 95% confidence interval (CI), 0.26 to 3.25; P = 0.904] in the Se (+MMI) and placebo (+MMI) groups, respectively. During a 12-week follow-up, 11 of 23 (48%) and 12 of 27 (44%) relapsed (OR 1.13; 95% CI, 0.29 to 2.66; P = 0.81) in the Se and placebo groups, respectively. Serum concentrations of Se and selenoprotein P were unrelated to response or recurrence rates. At week 36, 12 of 29 (41%) and 15 of 33 (45%) were responders and still in remission in the Se and placebo groups, respectively (OR 0.85; 95% CI, 0.31 to 2.32; P = 0.80). Serum levels of free triiodothyronine/free tetraiodothyronine, thyroid-stimulating hormone receptor antibody, prevalence of moderate to severe Graves orbitopathy, thyroid volume, and MMI starting dose were significantly lower in responders than in nonresponders. A total of 56 and 63 adverse events occurred in the Se and placebo groups, respectively (P = 0.164), whereas only one drug-related side effect (2.9%) was noted in 35 patients on placebo + MMI.
Conclusions: Supplemental Se did not affect response or recurrence rates in GD.
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