Adjuvant Treatment of Graves’ Hyperthyroidism with Selenium Yeast

Thyroid disease. Hyperthyroidism. Adjuvant treatment of thyroid disease with selenium yeast supplementation. All topics of interest. At this writing (August 2022), we await the publication of the outcomes of the GRASS clinical trial. GRASS is the acronym for the selenium supplementation for patients with Graves’ hyperthyroidism study [study protocol described by Watt 2013].

What is Graves’ Hyperthyroidism?

Thyroid gland
The thyroid gland is a butterfly-shaped endocrine gland in the neck below the Adam’s apple that makes and stores hormones that help regulate blood pressure, body temperature, heart rate, and the rate at which food is converted into energy. [This image is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.]
Hyperthyroidism is an autoimmune disease. It causes overactivity of the thyroid gland, resulting in too much production of the hormone thyroxine. Hyperthyroidism can cause an acceleration of the body’s metabolism; it can cause weight loss and rapid or irregular heartbeat.

Hyperthyroidism is caused by a number of conditions, including Graves’ disease, which is a common cause. Graves’ disease is the result of immune system disorder. It can affect anyone, but it is more common in women and in individuals under the age of 40.

Why Use Selenium Supplementation FOR Patients with Hyperthyroidism?

It is known that there is, normally, a high concentration of selenium in the thyroid gland. Moreover, several known selenoproteins – enzymes dependent upon a supply of selenium – are present in the thyroid gland.

Especially important are the selenoenzymes iodothyronine deiodinases, glutathione peroxidases, and thioredoxin reductases, which are involved in thyroid hormone metabolism and in protection from oxidative damage [Schomburg 2011].

Consequently, it is logical to think that supplementation with selenium may have beneficial effects on autoimmune hypothyroidism in particular and perhaps also on autoimmune hyperthyroidism [Watt 2013].

In the GRASS trial, the investigators seek to learn whether supplementation with selenium yeast in addition to standard treatment with anti-thyroid drugs will yield superior results to standard treatment with anti-thyroid drugs alone. That is to say, the investigators want to see whether the adjuvant selenium yeast therapy will be associated with the following outcomes in patients diagnosed with Graves’ hyperthyroidism:

  • a decrease in anti-thyroid drug treatment failure (defined as the failure to maintain normal thyroid function without further treatment one year after the cessation of the anti-thyroid drug treatment)
  • a faster and longer lasting remission
  • an improved quality of life
Selenium as an Adjuvant Therapy Together with Methimazole

Methimazole is a prescription drug that is used to treat hyperthyroidism (i.e., overactive thyroid) by preventing the thyroid gland from producing too much of the T3 and T4 thyroid hormones.

In this article, we review the outcomes of studies in which selenium yeast supplementation has been used as an adjuvant therapy to the main drug treatment using methimazole.

Adjuvant Treatment with Selenium and Vitamin D

In 2022, Gallo et al reported the results of a randomized controlled trial in which adjuvant supplementation with selenium and vitamin D together with methimazole treatment resulted in a prompter control of hyperthyroidism and a greater improvement in quality of life than did the methimazole monotherapy. The researchers speculated that using supplementation to reach optimal selenium and vitamin D levels was beneficial because the antioxidant selenoenzymes are needed to reduce oxidative stress and the vitamin D is needed for an adequate anti-inflammatory immune response [Gallo 2022].

In 2019, Xu et al reported the outcomes of a pilot study that suggested that the combined use of methimazole and selenium could improve the thyroid activity in patients and may be an effective therapy for the treatment of Graves’ disease [Xu 2019].

In 2018, Zheng et al reported the results of a meta-analysis and systematic review that showed that, compared to patients on placebos, patients on selenium supplementation were more likely than controls to show improved thyroid function after the first six months of treatment; however, the significantly better effect could not be seen after nine months of treatment. The reason is not clear [Zheng 2018].

Conclusion: Selenium Supplementation for Overactive Thyroid conditions
Adjuvant Therapy with Selenium for Autoimmune Thyroiditis

At this point, the efficacy of selenium supplementation in addition to standard medical treatment seems to be somewhat better demonstrated in the patients with hypothyroidism. In that respect, we await the publication of the results of the CATALYST clinical study [study protocol described in Winther 2014].

However, there is good reason and some evidence to believe that adjuvant selenium supplementation will benefit patients with hyperthyroidism, inter alia, the antioxidant effect of the selenoenzymes [Watt 2013].

Selenium-enriched Yeast Supplements Preferred

The reason for choosing a selenium-enriched yeast supplement is that supplementation with high-selenium yeast is associated with a reduction in oxidative stress levels whereas supplementation with supplements containing 100% selenomethionine is not [Richie 2014].


Gallo D, Mortara L, Veronesi G, Cattaneo SA, Genoni A, Gallazzi M, Peruzzo C, Lasalvia P, Moretto P, Bruno A, Passi A, Pini A, Nauti A, Lavizzari MA, Marinò M, Lanzolla G, Tanda ML, Bartalena L, Piantanida E. Add-On Effect of Selenium and Vitamin D Combined Supplementation in Early Control of Graves’ Disease Hyperthyroidism During Methimazole Treatment. Front Endocrinol (Lausanne). 2022 Jun 15;13:886451.

Richie JP Jr, Das A, Calcagnotto AM, Sinha R, Neidig W, Liao J, Lengerich EJ, Berg A, Hartman TJ, Ciccarella A, Baker A, Kaag MG, Goodin S, DiPaola RS, El-Bayoumy K. Comparative effects of two different forms of selenium on oxidative stress biomarkers in healthy men: a randomized clinical trial. Cancer Prev Res (Phila). 2014 Aug;7(8):796-804.

Schomburg L. Selenium, selenoproteins and the thyroid gland: interactions in health and disease. Nat Rev Endocrinol. 2011 Oct 18;8(3):160-71.

Watt T, Cramon P, Bjorner JB, Bonnema SJ, Feldt-Rasmussen U, Gluud C, Gram J, Hansen JL, Hegedüs L, Knudsen N, Bach-Mortensen P, Nolsøe R, Nygaard B, Pociot F, Skoog M, Winkel P, Rasmussen AK. Selenium supplementation for patients with Graves’ hyperthyroidism (the GRASS trial): study protocol for a randomized controlled trial. Trials. 2013 Apr 30;14:119.

Winther KH, Watt T, Bjørner JB, Cramon P, Feldt-Rasmussen U, Gluud C, Gram J, Groenvold M, Hegedüs L, Knudsen N, Rasmussen ÅK, Bonnema SJ. The chronic autoimmune thyroiditis quality of life selenium trial (CATALYST): study protocol for a randomized controlled trial. Trials. 2014 Apr 9;15:115.

Xu B, Wu D, Ying H, Zhang Y. A pilot study on the beneficial effects of additional selenium supplementation to methimazole for treating patients with Graves’ disease. Turk J Med Sci. 2019 Jun 18;49(3):715-722.

Zheng H, Wei J, Wang L, Wang Q, Zhao J, Chen S, Wei F. Effects of Selenium Supplementation on Graves’ Disease: A Systematic Review and Meta-Analysis. Evid Based Complement Alternat Med. 2018 Sep 26;2018:3763565.

The information presented in this review article is not intended as medical advice and should not be used as such.

15 September 2022

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