Iodine is essential for thyroid hormone synthesis — without it, you cannot produce T3 or T4. Our research shows that while overt deficiency (goiter, cretinism) is rare in iodized-salt countries, suboptimal iodine status is surprisingly common, particularly in pregnant women where even mild deficiency reduces child IQ by 6-10 points. The critical safety concern: both deficiency AND excess cause thyroid dysfunction. Supplementing >1,100mcg/day (the UL) can trigger thyroid autoimmunity, hypothyroidism, or hyperthyroidism — especially in populations with pre-existing thyroid disease. This is a supplement where more is definitively NOT better.
Iodine is the essential substrate for thyroid peroxidase (TPO), the enzyme that incorporates iodine into thyroglobulin to form T4 (thyroxine) and T3 (triiodothyronine). Without iodine, TPO has nothing to work with and thyroid hormone production stops. The thyroid gland actively concentrates iodine 20-50x above blood levels via the sodium-iodide symporter (NIS). In deficiency, the gland enlarges (goiter) trying to capture more iodine. In excess, the Wolff-Chaikoff effect temporarily halts hormone production, but chronic excess can permanently damage the gland, especially in those with anti-TPO antibodies (Hashimoto's).
Reviewed by the Scan Dose Research Team and Clinical Advisory Board | Last updated:
Not medical advice. Based on published clinical research and systematic reviews.