How does iodine help the thyroid gland make hormones?

Iodine is a fundamental component required for the production of thyroid hormones, specifically thyroxine and triiodothyronine. These hormones cannot be synthesized by the thyroid gland without it.12

The process of hormone synthesis involves several key steps:

• Uptake: Thyroid follicular cells actively concentrate inorganic iodide from the bloodstream.12
• Oxidation and Binding: The iodide is oxidized by an enzyme and attached to tyrosine residues within a glycoprotein called thyroglobulin.12
• Synthesis: These iodinated tyrosine residues are rearranged to form the active hormones. Thyroxine contains four iodine atoms, while triiodothyronine contains three.1
• Storage and Release: Thyroglobulin serves as the structural framework for this synthesis and as a storage reservoir for the hormones within the thyroid follicles. When needed, the gland breaks down the thyroglobulin to release the hormones into the circulation.12

Because iodine is essential for these biological processes, a deficiency can lead to decreased hormone production, which may trigger the pituitary gland to stimulate thyroid growth, potentially resulting in goitre.32