Selenium Supplementation in Patients with Hashimoto Thyroiditis: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Background: Hashimoto thyroiditis (HT) is the most common cause of hypothyroidism in iodine-sufficient areas. Selenium is an essential trace element required for thyroid hormone synthesis and exerts antioxidant effects. Therefore, it may be of relevance in the management of HT. Methods: We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate the effect of selenium supplementation on thyroid function (thyrotropin [TSH], free and total thyroxine [fT4, T4], free and total triiodothyronine [fT3, T3]), thyroid antibodies (thyroid peroxidase antibodies [TPOAb], thyroglobulin antibodies [TGAb], thyrotropin receptor antibody [TRAb]), ultrasound findings (echogenicity, thyroid volume), immune markers, patient-reported outcomes, and adverse events in HT. The study protocol was registered on PROSPERO (CRD42022308377). We systematically searched MEDLINE, Embase, CINHAL, Web of Science, Google Scholar, and the Cochrane CENTRAL Register of Trials from inception to January 2023 and searched citations of eligible studies. Two independent authors reviewed and coded the identified literature. The primary outcome was TSH in patients without thyroid hormone replacement therapy (THRT); the others were considered secondary outcomes. We synthesized the results as standardized mean differences (SMD) or odds ratio (OR), assessed risk of bias using the Cochrane RoB 2 tool, and rated the evidence using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Results: We screened 687 records and included 35 unique studies. Our meta-analysis found that selenium supplementation decreased TSH in patients without THRT (SMD -0.21 [confidence interval, CI -0.43 to -0.02]; 7 cohorts, 869 participants; I2 = 0%). In addition, TPOAb (SMD -0.96 [CI -1.36 to -0.56]; 29 cohorts; 2358 participants; I2 = 90%) and malondialdehyde (MDA; SMD -1.16 [CI -2.29 to -0.02]; 3 cohorts; 248 participants; I2 = 85%) decreased in patients with and without THRT. Adverse effects were comparable between the intervention and control groups (OR 0.89 [CI 0.46 to 1.75]; 16 cohorts; 1339 participants; I2 = 0%). No significant changes were observed in fT4, T4, fT3, T3, TGAb, thyroid volume, interleukin (IL)-2, and IL-10. Overall, certainty of evidence was moderate. Conclusions: In people with HT without THRT, selenium was effective and safe in lowering TSH, TPOAb, and MDA levels. Indications for lowering TPOAb were found independent of THRT.

Do Dietary Supplements Affect Inflammation, Oxidative Stress, and Antioxidant Status in Adults with Hypothyroidism or Hashimoto's Disease?-A Systematic Review of Controlled Trials

This systematic review aims to summarise the results of controlled trials on dietary supplements (DS) usage and inflammation, oxidative stress, antioxidant status, and thyroid parameter improvement in hypothyroidism (HT)/Hashimoto's thyroiditis (AIT) patients. The study protocol was registered with PROSPERO (no. CRD42022365149). A comprehensive search of the PubMed, Scopus, and Web of Science databases resulted in the identification of nineteen randomised controlled trials and three non-randomised studies for the review; three studies examined the effect of supplementation with vitamin D, twelve studies-with selenium, and seven studies-with other DS. Based on very limited evidence, the lack of influence of vitamin D supplementation on inflammatory parameters was found, while no studies have examined oxidative stress and antioxidant status parameters, and only one provided results for a single thyroid parameter after an intervention. Some evidence was found proving that selenium supplementation may decrease inflammation and improve thyroid parameters, but reaching a conclusion about its influence on oxidative stress and antioxidant status is not possible because of the insufficient number of studies. Additionally, due to examining other DS (e.g., multicomponent, Nigella sativa, and genistein) only in single studies, conclusions cannot be drawn. Further long-term, high-quality randomised controlled trials are necessary to better understand the influence of DS on inflammation, oxidative stress, and antioxidant status, as well as their potential to improve thyroid gland function in HT/AIT patients.

Serum selenium status in Graves' disease and Hashimoto's thyroiditis in an iodine-sufficient area: A case-control study

Background

Selenium (Se) can be found in the molecular structure of selenoproteins; including thioredoxin reductase and glutathione peroxidase and also in Type I and II deiodinases. Previous studies have shown that Se deficiency has been linked to autoimmune thyroid disease (AITD). In the present study, we investigated the serum Se levels of patients with Graves' disease (GD), Hashimoto's thyroiditis (HT), and euthyroid individuals as a control group.

Materials and Methods

The present study was performed on patients with newly diagnosed AITD (GD and HT). The control group was matched with the case group in terms of parameters such as age and sex. Free thyroxine, free triiodothyronine, thyroid-stimulating hormone, antithyroid peroxidase, antithyroglobulin, and serum Se levels were measured in all participants. These parameters were compared between groups.

Results

Data from 132 patients with HT, 120 patients with GD, and 120 healthy euthyroid patients as a control group were analyzed. The Se level in patients with HT (104.36 μg/l) and GD (97.68 μg/l) was significantly lower than in the control group (122.63 μg/l) (P < 0.001). The incidence of Se deficiency in patients with HT, GD, and in the control group was 15.2%, 2.5%, and 2.5%, respectively (P < 0.001). In patients with GD, 34 patients (28.33%) had Graves' orbitopathy. Se levels in patients with orbitopathy were significantly lower than in patients without orbitopathy.

Conclusion

The serum Se level was significantly lower in newly diagnosed patients with GD and HT than in the control group. Overall, Se deficiency can be considered a risk factor for AITDs.