Supplementary Material for: A Prospective Investigation of Graves' Disease and Selenium: Thyroid Hormones, Auto-Antibodies and Self-Rated Symptoms

<b><i>Background:</i></b> In Graves' thyrotoxicosis tachycardia, weight loss and mental symptoms are common. Recovery takes time and varies between patients. Treatment with methimazole reduces thyroid hormone levels. According to previous research, this reduction has been faster if selenium (Se) is added. <b><i>Objective:</i></b> The objective was to investigate whether supplementing the pharmacologic treatment with Se could change the immune mechanisms, hormone levels and/or depression and anxiety. <b><i>Methods:</i></b> We prospectively investigated 38 patients with initially untreated thyrotoxicosis by measuring the thyroid-stimulating hormone (TSH), free thyroxine (FT<sub>4</sub>), free triiodothyronine (FT<sub>3</sub>), thyroid receptor antibodies and thyroid peroxidase auto-antibodies before medication and at 6, 18 and 36 weeks after commencing treatment with methimazole and levo-thyroxine, with a randomized blinded oral administration of 200 µg Se/day or placebo. The selenoprotein P concentration was determined in plasma at inclusion and after 36 weeks. The patients were also assessed with questionnaires about depression, anxiety and self-rated symptoms before medication was started and after 36 weeks. <b><i>Results:</i></b> FT<sub>4</sub> decreased more in the Se group at 18 weeks (14 vs. 17 pmol/l compared to the placebo group, p = 0.01) and also at 36 weeks (15 vs. 18 pmol/l, p = 0.01). The TSH increased more in the Se group at 18 weeks (0.05 vs. 0.02 mIU/l, p = 0.04). The depression and anxiety scores were similar in both groups. In the Se group, the depression rates correlated negatively with FT<sub>3</sub> and positively with TSH. This was not seen in the placebo group. <b><i>Conclusions:</i></b> Se supplementation can enhance biochemical restoration of hyperthyroidism, but whether this could shorten clinical symptoms of thyrotoxicosis and reduce mental symptoms must be investigated further.