Trace elements in the internal environment and the hormone-producing capacity of the thyroid gland: a systematic review

Abstract

Background Trace elements are needed for the normal functioning of the thyroid. Elements such as selenium, zinc, copper, iron, manganese, and iodine are involved in thyroid hormone synthesis and metabolism and in protecting thyroid tissue from oxidative damage. Trace elements act as cofactors for antioxidant enzymes, helping to regulate oxidative stress in the body. An imbalance between oxidative and antioxidant processes is considered a contributing factor in several thyroid disorders, including autoimmune thyroid diseases and thyroid tumours. When trace element levels become deficient or excessive, this balance can be disrupted, potentially leading to impaired thyroid hormone production and altered thyroid hormone status. Purpose This study aims to systematically review the current knowledge concerning the effect of trace elements on the redox regulation of thyroid hormonogenesis and the development of thyroid diseases. Methods Literature searches were carried out following the PECO framework across PubMed, ScienceDirect, Springer, Nature, ResearchGate, Scopus, and Google Scholar databases to identify English-language Cross-sectional, Case-control, Prospective cohort, Randomized controlled trial, and Comparative studies meeting the inclusion criteria. All available studies published between 2015 and 2025 were included. Results Imbalances in these elements were associated with changes in thyroid hormone levels, variations in thyroid gland volume, and an elevated risk of nodular thyroid disease and autoimmune thyroid disorders. Across the reviewed studies, trace element imbalances were shown to affect important enzymes related to the thyroid, such as thyroid peroxidase, iodothyronine deiodinases, glutathione peroxidase, and other antioxidant enzymes. Selenium and iron were identified as the most consistently correlated elements with indices of thyroid hormone status and glandular capacity. Conclusion The findings show that the clinical relevance of trace element status for thyroid health is context-dependent, varying with iodine sufficiency, radiation exposure, sex, age and occupational profile. Stratified screening and intervention strategies, rather than uniform population recommendations, are needed to translate this evidence into improved thyroid care and public well-being. Clinical trial number Not applicable.