Consequences of excess iodine

Journal name:
Nature Reviews Endocrinology
Year published:
Published online


Iodine is a micronutrient that is essential for the production of thyroid hormones. The primary source of iodine is the diet via consumption of foods that have been fortified with iodine, including salt, dairy products and bread, or that are naturally abundant in the micronutrient, such as seafood. Recommended daily iodine intake is 150 µg in adults who are not pregnant or lactating. Ingestion of iodine or exposure above this threshold is generally well-tolerated. However, in certain susceptible individuals, including those with pre-existing thyroid disease, the elderly, fetuses and neonates, or patients with other risk factors, the risk of developing iodine-induced thyroid dysfunction might be increased. Hypothyroidism or hyperthyroidism as a result of supraphysiologic iodine exposure might be either subclinical or overt, and the source of the excess iodine might not be readily apparent.


  1. Food and Nutrition Board, Institute of Medicine in Dietary Reference Intakes 320327 (National Academy Press, Washington, D. C., 2006).
  2. WHO, UNICEF and ICCIDD. Assessment of the iodine deficiency disorders and monitoring their elimination. WHO/NHD/01.1 [online], (2007).
  3. Rasmussen, L. B., Ovesen, L. & Christiansen, E. Day-to-day and within-day variation in urinary iodine excretion. Eur. J. Clin. Nutr. 53, 401407 (1999).
  4. Zimmermann, M. B. et al. Assessment of iodine status using dried blood spot thyroglobulin: development of reference material and establishment of an international reference range in iodine-sufficient children. J. Clin. Endocrinol. Metab. 91, 48814887 (2006).
  5. Zimmermann, M. B. et al. Thyroglobulin is a sensitive measure of both deficient and excess iodine intakes in children and indicates no adverse effects on thyroid function in the UIC range of 100–299 µg/l: a UNICEF/ICCIDD study group report. J. Clin. Endocrinol. Metab. 98, 12711280 (2013).
  6. Wolff, J. & Chaikoff, I. L. Plasma inorganic iodide as a homeostatic regulator of thyroid function. J. Biol. Chem. 174, 555564 (1948).
  7. Pramyothin, P., Leung, A. M., Pearce, E. N., Malabanan, A. O. & Braverman, L. E. Clinical problem-solving. A hidden solution. N. Engl. J. Med. 365, 21232127 (2011).
  8. Eng, P. H. et al. Escape from the acute Wolff–Chaikoff effect is associated with a decrease in thyroid sodium/iodide symporter messenger ribonucleic acid and protein. Endocrinology 140, 34043410 (1999).
  9. Dai, G., Levy, O. & Carrasco, N. Cloning and characterization of the thyroid iodide transporter. Nature 379, 458460 (1996).
  10. Saberi, M. & Utiger, R. D. Augmentation of thyrotropin responses to thyrotropin-releasing hormone following small decreases in serum thyroid hormone concentrations. J. Clin. Endocrinol. Metab. 40, 435441 (1975).
  11. Safran, M. & Braverman, L. E. Effect of chronic douching with polyvinylpyrrolidone-iodine on iodine absorption and thyroid function. Obstet. Gynecol. 60, 3540 (1982).
  12. Paul, T. et al. The effect of small increases in dietary iodine on thyroid function in euthyroid subjects. Metabolism 37, 121124 (1988).
  13. Bahn, R. S. et al. Hyperthyroidism and other causes of thyrotoxicosis: Management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists. Thyroid 21, 593646 (2011).
  14. Coindet, J. F. Nouvelles recherches sur les effets de l'iode, et sur les precautions a suivre dans le traitement de goitre par le nouveau remede [French]. Ann. Chim. Phys. 16, 252256 (1821).
  15. Vagenakis, A. G. et al. Iodide-induced thyrotoxicosis in Boston. N. Engl. J. Med. 287, 523527 (1972).
  16. International Council for the Control of Iodine Deficiency Disorders [online], (2013).
  17. Zimmermann, M. B., Jooste, P. L. & Pandav, C. S. Iodine-deficiency disorders. Lancet 372, 12511262 (2008).
  18. Goyle, A. & Prakash, S. Efficacy of multi-micronutrient fortified biscuits on urinary iodine levels of adolescent girls from Jaipur, India. Malays. J. Nutr. 17, 143150 (2011).
  19. Kassim, I. A. et al. Excessive iodine intake during pregnancy in Somali refugees. Matern. Child. Nutr. 8, 4956 (2012).
  20. Sang, Z. et al. Exploration of the safe upper level of iodine intake in euthyroid Chinese adults: a randomized double-blind trial. Am. J. Clin. Nutr. 95, 367373 (2012).
  21. Laurberg, P. et al. The Danish investigation on iodine intake and thyroid disease, DanThyr: status and perspectives. Eur. J. Endocrinol. 155, 219228 (2006).
  22. Thomson, C. D., Campbell, J. M., Miller, J. & Skeaff, S. A. Minimal impact of excess iodate intake on thyroid hormones and selenium status in older New Zealanders. Eur. J. Endocrinol. 165, 745752 (2011).
  23. Galofre, J. C., Fernandez-Calvet, L., Rios, M. & Garcia-Mayor, R. V. Increased incidence of thyrotoxicosis after iodine supplementation in an iodine sufficient area. J. Endocrinol. Invest. 17, 2327 (1994).
  24. Todd, C. H. et al. Increase in thyrotoxicosis associated with iodine supplements in Zimbabwe. Lancet 346, 15631564 (1995).
  25. Parveen, S., Latif, S. A., Kamal, M. M. & Uddin, M. M. Effects of long term iodized salt consumption on serum T3, T4 and TSH in an iodine deficient area of Bangladesh. Mymensingh Med. J. 16, 5760 (2007).
  26. Allen, E. M., Appel, M. C. & Braverman, L. E. The effect of iodine ingestion on the development of spontaneous lymphocytic thyroiditis in the diabetes-prone BB/W rat. Endocrinology 118, 19771998 (1986).
  27. Kahaly, G. J., Dienes, H. P., Beyer, J. & Hommel, G. Iodide induces thyroid autoimmunity in patients with endemic goiter: a randomized, double-blind, placebo-controlled trial. Eur. J. Endocrinol. 139, 290297 (1998).
  28. Dong, W. et al. The changing incidence of thyroid carcinoma in Shenyang, China before and after universal salt iodization. Med. Sci. Monit. 19, 4953 (2013).
  29. Blomberg, M., Feldt-Rasmussen, U., Andersen, K. K. & Kjaer, S. K. Thyroid cancer in Denmark 1943–2008, before and after iodine supplementation. Int. J. Cancer 131, 23602366 (2012).
  30. Murray, C. W., Egan, S. K., Kim, H., Beru, N. & Bolger, P. M. US Food and Drug Administration's Total Diet Study: dietary intake of perchlorate and iodine. J. Expo. Sci. Environ. Epidemiol. 18, 571580 (2008).
  31. Perrine, C. G., Sullivan, K. M., Flores, R., Caldwell, K. L. & Grummer-Strawn, L. M. Intakes of dairy products and dietary supplements are positively associated with iodine status among U. S. children. J. Nutr. 143, 11551160 (2013).
  32. Clifton, V. L. et al. The impact of iodine supplementation and bread fortification on urinary iodine concentrations in a mildly iodine deficient population of pregnant women in South Australia. Nutr. J. 12, 32 (2013).
  33. Zimmermann, M. B. Iodine deficiency. Endocr. Rev. 30, 376408 (2009).
  34. Zava, T. T. & Zava, D. T. Assessment of Japanese iodine intake based on seaweed consumption in Japan: a literature-based analysis. Thyroid Res. 4, 1420 (2011).
  35. Rhee, S. S., Braverman, L. E., Pino, S., He, X. & Pearce, E. N. High iodine content of Korean seaweed soup: a health risk for lactating women and their infants? Thyroid 21, 927928 (2011).
  36. Teas, J., Pino, S., Critchley, A. & Braverman, L. E. Variability of iodine content in common commercially available edible seaweeds. Thyroid 14, 836841 (2004).
  37. Mussig, K. et al. Iodine-induced thyrotoxicosis after ingestion of kelp-containing tea. J. Gen. Intern. Med. 21, C11C14 (2006).
  38. Eliason, B. C. Transient hyperthyroidism in a patient taking dietary supplements containing kelp. J. Am. Board Fam. Pract. 11, 478480 (1998).
  39. Teas, J. et al. Seaweed and soy: companion foods in Asian cuisine and their effects on thyroid function in American women. J. Med. Food 10, 90100 (2007).
  40. Miyai, K., Tokushige, T., Kondo, M. & Iodine Research Group. Suppression of thyroid function during ingestion of seaweed “Kombu” (Laminaria japonoca) in normal Japanese adults. Endocr. J. 55, 11031108 (2008).
  41. Kasahara, T. et al. Delayed onset congenital hypothyroidism in a patient with DUOX2 mutations and maternal iodine excess. Am. J. Med. Genet. A. 161A, 214217 (2013).
  42. Fuse, Y., Saito, N., Tsuchiya, T., Shishiba, Y. & Irie, M. Smaller thyroid gland volume with high urinary iodine excretion in Japanese schoolchildren: normative reference values in an iodine-sufficient area and comparison with the WHO/ICCIDD reference. Thyroid 17, 145155 (2007).
  43. Konno, N., Makita, H., Iizuka, N. & Kawasaki, K. Association between dietary iodine intake and prevalence of subclinical hypothyroidism in the coastal regions of Japan. J. Clin. Endocrinol. Metab. 78, 393397 (1994).
  44. Michikawa, T. et al. Seaweed consumption and the risk of thyroid cancer in women: the Japan Public Health Center-based Prospective Study. Eur. J. Cancer Prev. 21, 254260 (2012).
  45. Dasgupta, P. K., Liu, Y. & Dyke, J. V. Iodine nutrition: iodine content of iodized salt in the United States. Environ. Sci. Technol. 42, 13151323 (2008).
  46. Leung, A. M., Pearce, E. N. & Braverman, L. E. Iodine content of prenatal multivitamins in the United States. N. Engl. J. Med. 360, 939940 (2009).
  47. Connelly, K. J. et al. Congenital hypothyroidism caused by excess prenatal maternal iodine ingestion. J. Pediatr. 161, 760762 (2012).
  48. Nishiyama, S. et al. Transient hypothyroidism or persistent hyperthyrotropinemia in neonates born to mothers with excessive iodine intake. Thyroid 14, 10771083 (2004).
  49. Emder, P. J. & Jack, M. M. Iodine-induced neonatal hypothyroidism secondary to maternal seaweed consumption: a common practice in some Asian cultures to promote breast milk supply. J. Paediatr. Child Health 47, 750752 (2011).
  50. Shumer, D. E., Mehringer, J. E., Braverman, L. E. & Dauber, A. Acquired Hypothyroidism in an Infant Related to Excessive Maternal Iodine Intake: Food for Thought. Endocr. Pract. 9, 729731 (2013).
  51. American Thyroid Association. ATA Statement on the Potential Risks of Excess Iodine Ingestion and Exposure [online], (2013).
  52. Minelli, R., Gardini, E., Bianconi, L., Salvi, M. & Roti, E. Subclinical hypothyroidism, overt thyrotoxicosis and subclinical hypothyroidism: the subsequent phases of thyroid function in a patient chronically treated with amiodarone. J. Endocrinol. Invest. 15, 853855 (1992).
  53. Danzi, S. & Klein, I. Amiodarone-induced thyroid dysfunction. J. Intensive Care Med.
  54. Bogazzi, F., Tomisti, L., Bartalena, L., Aghini-Lombardi, F. & Martino, E. Amiodarone and the thyroid: a 2012 update. J. Endocrinol. Invest. 35, 340348 (2012).
  55. Eskes, S. A. et al. Treatment of amiodarone-induced thyrotoxicosis type 2: a randomized clinical trial. J. Clin. Endocrinol. Metab. 97, 499506 (2012).
  56. Tomisti, L. et al. Total thyroidectomy in patients with amiodarone-induced thyrotoxicosis and severe left ventricular systolic dysfunction. J. Clin. Endocrinol. Metab. 97, 35153521 (2012).
  57. Bogazzi, F. et al. Preparation with iopanoic acid rapidly controls thyrotoxicosis in patients with amiodarone-induced thyrotoxicosis before thyroidectomy. Surgery 132, 11141117 (2002).
  58. Bogazzi, F. et al. Color flow Dopploer sonography rapidly differentiates type I and type II amiodarone-induced thyrotoxicosis. Thyroid 7, 541545 (1997).
  59. Tomisti, L. et al. Effects of amiodarone, thyroid hormones and CYP2C9 and VKORC1 polymorphisms on warfarin metabolism: a review of the literature. Endocr. Pract. 19, 10431049 (2013).
  60. Rhee, C. M., Bhan, I., Alexander, E. K. & Brunelli, S. M. Association between iodinated contrast media exposure and incident hyperthyroidism and hypothyroidism. Arch. Intern. Med. 172, 153159 (2012).
  61. Nimmons, G. L., Funk, G. F., Graham, M. M. & Pagedar, N. A. Urinary iodine excretion after contrast computed tomography scan: implications for radioactive iodine use. JAMA Otolaryngol. Head Neck Surg. 139, 479482 (2013).
  62. Padovani, R. P. et al. One month is sufficient for urinary iodine to return to its baseline value after the use of water-soluble iodinated contrast agents in post-thyroidectomy patients requiring radioiodine therapy. Thyroid 22, 926930 (2012).
  63. Alkhuja, S., Pyram, R. & Odeyemi, O. In the eye of the storm: Iodinated contrast medium induced thyroid storm presenting as cardiopulmonary arrest. Heart Lung 42, 267269 (2013).
  64. Gartner, W. & Weissel, M. Do iodine-containing contrast media induce clinically relevant changes in thyroid function parameters of euthyroid patients within the first week? Thyroid 14, 521524 (2004).
  65. Koroscil, T. M., Pelletier, P. R., Slauson, J. W. & Hennessey, J. Short-term effects of coronary angiographic contrast agents on thyroid function. Endocr. Pract. 3, 219221 (1997).
  66. Ozkan, S. et al. Thyroid functions after contrast agent administration for coronary angiography: a prospective observational study in euthyroid patients. Anadolu Kardiyol Derg. 13, 363369 (2013).
  67. Kochi, M. H., Kaloudis, E. V., Ahmed, W. & Moore, W. H. Effect of in utero exposure of iodinated intravenous contrast on neonatal thyroid function. J. Comput. Assist. Tomogr. 36, 165169 (2012).
  68. Thaker, V., Levine, B.-S., Leung, A. M. & Braverman, L. E. Neonatal iodine-induced hypothyroidism after cardiac arteriography. Presented at ENDO2013.
  69. Conn, J. J., Sebastian, M. J., Deam, D., Tam, M. & Martin, F. I. A prospective study of the effect of nonionic contrast media on thyroid function. Thyroid 6, 107110 (1996).
  70. Martin, F. I., Tress, B. W., Colman, P. G. & Deam, D. R. Iodine-induced hyperthyroidism due to nonionic contrast radiography in the elderly. Am. J. Med. 95, 7882 (1993).
  71. van der Molen, A. J., Thomsen, H. S., Morcos, S. K. & Contrast Media Safety Committee, European Society of Urogenital Radiology (ESUR). Effect of iodinated contrast media on thyroid function in adults. Eur. Radiol. 14, 902907 (2004).
  72. Gordon, C. M., Rowitch, D. H., Mitchell, M. L. & Kohane, I. S. Topical iodine and neonatal hypothyroidism. Arch. Pediatr. Adolesc. Med. 149, 13361339 (1995).
  73. Linder, N. et al. Topical iodine-containing antiseptics and subclinical hypothyroidism in preterm infants. J. Pediatr. 131, 434439 (1997).
  74. Vermeulen, H. et al. Benefit and harm of iodine in wound care: a systematic review. J. Hosp. Infect. 76, 191199 (2010).
  75. Ader, A. W. et al. Effect of mouth rinsing with two polyvinylpyrrolidone-iodine mixtures on iodine absorption and thyroid function. J. Clin. Endocrinol. Metab. 66, 632635 (1988).
  76. McMonigal, K. A. et al. Thyroid function changes related to use of iodinated water in the U. S.Space Program. Aviat. Space Environ. Med. 71, 11201125 (2000).
  77. Georgitis, W. J., McDermott, M. T. & Kidd, G. S. An iodine load from water-purification tablets alters thyroid function in humans. Mil. Med. 158, 794797 (1993).
  78. Pearce, E. N. et al. Effects of chronic iodine excess in a cohort of long-term American workers in West Africa. J. Clin. Endocrinol. Metab. 87, 54995502 (2002).
  79. Nauman, J. & Wolff, J. Iodide prophylaxis in Poland after the Chernobyl reactor accident: benefits and risks. Am. J. Med. 94, 524532 (1993).
  80. Pearce, E. N., Pino, S., Bazrafshan, H. R., Lee, S. L. & Braverman, L. E. Sources of dietary iodine: bread, cows' milk, and infant formula in the Boston area. J. Clin. Endocrinol. Metab. 89, 34213424 (2004).
  81. Allegrini, M., Pennington, J. A. T. & Tanner, J. T. Total diet study: determination of iodine intake by neutron activation analysis. J. Am. Diet. Assoc. 83, 1824 (1983).

Download references

Author information


  1. Division of Endocrinology, Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, VA Greater Los Angeles Healthcare System, 11301 Wilshire Boulevard (111D), Los Angeles, CA 90073, USA.

    • Angela M. Leung
  2. Section of Endocrinology, Diabetes, and Nutrition, Department of Medicine, Boston University School of Medicine, 88 East Newton Street, Evans 201, Boston, MA 02118, USA.

    • Lewis E. Braverman


Both authors contributed equally to all aspects of this manuscript.

Competing interests statement

The authors declare no competing interests.

Corresponding author

Correspondence to:

Author details

  • Angela M. Leung

    Angela M. Leung, MD, MSc, is Assistant Clinical Professor of Medicine in the Division of Endocrinology, University of California Los Angeles, USA. She received a BA at Occidental College, USA, an MD from Boston University School of Medicine, USA, and an MSc from Boston University School of Public Health, USA. She completed her medicine residency and endocrinology fellowship training at Boston University School of Medicine and Boston Medical Center. Her clinical and research interests are in iodine nutrition, thyroid dysfunction and thyroid cancer, women and infant health, and environmental exposures that affect iodine nutrition.

  • Lewis E. Braverman

    Lewis E. Braverman, MD, is Professor of Medicine in the Section of Endocrinology, Diabetes, and Nutrition, Boston University School of Medicine, USA. He received his undergraduate degree from Harvard College, USA, and his MD from Johns Hopkins, USA. His residency and fellowship training was completed at the Thorndike Memorial Laboratory, Harvard Medical School, USA. Dr Braverman has held many leadership roles in national endocrine organizations and has published extensively in various aspects of thyroid physiology and pathophysiology.

Additional data