Effects of Magnesium Coadministration on Thyroid Function and Autoantibody Titers in Euthyroid Hashimoto’s Thyroiditis

Objective: Although magnesium (Mg) is integral to numerous metabolic and immunological processes, its influence in Hashimoto’s thyroiditis (HT) has not been fully elucidated. The present study sought to examine the effects of oral Mg supplementation on thyroid function and thyroid autoantibody in hypomagnesemic, euthyroid individuals with HT who were receiving a stable levothyroxine (LT4) regimen.Methods: In this retrospective observational analysis, adult patients with HT who were euthyroid and had documented hypomagnesemia were evaluated after receiving oral Mg supplementation for a minimum of two months, during which LT4 dosing remained unchanged. Serum thyroid-stimulating hormone (TSH), free thyroxine (fT4), free triiodothyronine (fT3), anti-thyroid peroxidase (anti-TPO), anti-thyroglobulin (anti-TG), and Mg levels were measured both prior to and following supplementation. Pre- and post-treatment values were compared using paired statistical methods.Results: A total of 45 patients (82% female, mean age 49.3 ± 15.7 years) were analyzed. All patients received oral Mg oxide equivalent to 365 mg elemental Mg daily. After two months of Mg supplementation, serum Mg levels increased significantly (p = 0.04). Serum TSH levels also showed a statistically significant increase (p = 0.03), while remaining within the euthyroid range. No significant changes were observed in fT4, fT3, anti-TPO, or anti-TG titers.Conclusion: In hypomagnesemic euthyroid patients with HT on stable LT4 therapy, short-term Mg supplementation was associated with a modest but significant increase in TSH without alterations in thyroid hormone levels or autoantibody titers. These findings suggest that Mg replacement may influence biochemical thyroid regulation without short-term effects on thyroid autoimmunity.