Thyroid hormone production
Iodine is incorporated into thyroxine (T4) and triiodothyronine (T3) by the thyroid gland. These hormones regulate basal metabolic rate, protein synthesis, and nearly every organ system in the body.
Metabolic regulation
Thyroid hormones control metabolic rate, body temperature, heart rate, and energy utilization. Adequate iodine prevents hypothyroidism-related fatigue, weight gain, and cold intolerance.
Fetal brain development
Iodine is critical during the first trimester when the fetal thyroid is not yet functional. Severe deficiency causes cretinism; mild deficiency impairs IQ and cognitive development.
Antioxidant activity
Iodide acts as an electron donor in cellular antioxidant reactions and may help neutralize hydrogen peroxide produced during thyroid hormone synthesis, protecting thyroid tissue.
Thyroid hormone synthesis
Iodide is actively transported into thyroid follicular cells by the sodium-iodide symporter, oxidized by thyroid peroxidase (TPO), and incorporated into tyrosine residues on thyroglobulin to form T3 and T4.
HPT axis regulation
Thyroid hormone levels are tightly controlled by the hypothalamic-pituitary-thyroid (HPT) axis. Low T3/T4 triggers TSH release, stimulating thyroid iodine uptake and hormone synthesis. Iodine deficiency leads to compensatory goiter formation.
RCT of iodine supplementation vs. placebo in 184 mildly iodine-deficient children in New Zealand over 28 weeks.
184 children aged 10–13. 28-week intervention.
Iodine supplementation significantly improved perceptual reasoning and cognitive processing scores. Underscores importance of adequate iodine even in mild deficiency states.