Background: The thyroid gland is a cornerstone of the endocrine system, regulating metabolism, growth, and development through its synthesis of thyroid hormones. The micronutrient iodine is an indispensable component of these hormones, and its availability is a critical determinant of thyroid health. Both deficiency and excess of iodine can lead to a spectrum of thyroid pathologies, representing a significant global health challenge.

Objective: This review aims to provide a comprehensive analysis of the intricate relationship between iodine and thyroid function. It synthesizes evidence on iodine metabolism, dietary requirements, the pathophysiology of iodine-related disorders, and the public health strategies implemented to mitigate them.

Methods: A systematic literature review was conducted, analyzing 56 seminal and contemporary research articles. The selected literature covers the foundational biochemistry of thyroid hormone synthesis, the epidemiology of iodine deficiency disorders (IDD), the neurodevelopmental consequences of iodine insufficiency, the impact of environmental and dietary goitrogens, and the global outcomes of salt iodization programs.

Results: The synthesis of the literature confirms that iodine uptake is a tightly regulated process involving the sodium-iodide symporter (NIS) and pendrin. Iodine deficiency is causally linked to hypothyroidism, goiter, and cretinism, with profound, irreversible effects on fetal and childhood neurodevelopment. Factors such as perchlorates, thiocyanates, and deficiencies in selenium and iron can exacerbate iodine-related disorders. While universal salt iodization has been a landmark public health success, challenges remain, including monitoring population iodine status, addressing deficiencies in vulnerable groups (e.g., pregnant women, vegans), and managing the risks of iodine-induced hyperthyroidism in previously deficient populations.

Conclusion: Maintaining optimal iodine nutrition is paramount for the prevention of thyroid pathologies. Effective and continuous monitoring of salt iodization programs and public education are essential to eradicate iodine deficiency disorders and ensure global thyroid health.

Thyroid Gland, Iodine Deficiency Disorders (IDD), Goiter, Cretinism

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