Clinical Question

Does a gluten-free diet reduce the symptoms of autoimmune thyroid disease?

Evidence-Based Answer

There is no evidence that following a gluten-free diet reduces symptoms of autoimmune thyroid disease. However, following a gluten-free diet may decrease mean thyroid-stimulating hormone (TSH) levels. (Strength of Recommendation [SOR]: C, disease-oriented evidence in a randomized controlled trial.) In women who are euthyroid and drug-naive with chronic autoimmune thyroid disease, following a gluten-free diet decreases antithyroid peroxidase and anti-thyroglobulin antibodies by 24% compared with increased levels in women following a regular diet. (SOR: C, nonrandomized trial with disease-oriented outcomes.)

Evidence Summary

A 2021 randomized controlled trial (n = 92) performed at an outpatient endocrinolog y clinic compared the effects of a gluten-free diet with a gluten-containing diet in patients with Hashimoto thyroiditis.¹ The trial included women 18 to 55 years of age with Hashimoto thyroiditis diagnosed by the presence of antithyroid peroxidase, antithyroglobulin antibodies, and reduced echogenicity on thyroid gland ultrasonography. Exclusion criteria were having malabsorptive diseases, already following a gluten-free diet, any history of gastrointestinal tract resection, any thyroid gland removal, Graves disease, diabetes mellitus, hypertension, smoking, and the use of glucocorticoids, statins, or nonsteroidal anti-inflammatory drugs. All patients followed a regular gluten-containing diet for three months before enrolling in the study and then were assigned to follow a gluten-free diet (less than 20 mg of gluten; n = 31) or a regular diet (n = 31) consisting of at least 10 g of gluten daily. The 30 remaining patients did not complete the study due to reasons such as inability to follow the prescribed diet. Only patients who completed at least three visits were included in the analysis. All 62 participants received levothyroxine, but dosing changes were not discussed during the study. The gluten-free diet group received follow-up appointments with clinical dietitians who analyzed patients' food diaries to ensure compliance with the gluten-free diet; patients also received education on the proper distribution of macronutrients.