Supplementation of iron, selenium, zinc and iodine in hypothyroidism

Aims: Hypothyroidism is a disease that affects numerous people all over the world. The treatment is based on supplementation of thyroid hormones, however recent clinical trials, meta-analyses, and systematic reviews provide new insights about the role of micronutrients in this disease. Nevertheless, there are inconsistencies in the literature regarding the efficacy and necessity of supplementing these micronutrients in patients with hypothyroidism. The motivation to broach this topic was the dynamic growth of the dietary supplements market and the interest we observed among patients regarding the use of supplements in our clinical practice. Our goal is to evaluate the latest literature regarding the role of supplementation of iron, selenium, zinc and iodine in patients with hypothyroidism and its practical significance for healthcare professionals. Methods: The literature review was conducted using the PubMed and Google Scholar database. Publications from 2016–2024 were searched using specific keywords. Results: Hypothyroidism negatively affects iron metabolism, conversely iron deficiency impacts negatively the thyroid function. However, we have found only one prospective study showing benefits of iron supplementation in hypothyroidism patients. Selenium supplementation in hypothyroidism reduces TSH levels, this effect is intensified by co-supplementation of myo-inositol. No impact of selenium supplementation on T3 and T4 levels was described; also the impact on quality of life is controversial. There is still a lack of definitive evidence regarding the positive effects of zinc supplementation in hypothyroidism. Although both iodine deficiency and excessive iodine intake can lead to hypothyroidism, the impact of iodine supplementation specifically in patients with hypothyroidism remains unclear. Conclusions: The microelements have clinical impact on function, metabolism and conversion of thyroid hormones; however the effectiveness of supplementation in hypothyroidism has not been broadly examined.