Horm Metab Res 2005; 37(9): 555-558
DOI: 10.1055/s-2005-870423
© Georg Thieme Verlag KG Stuttgart · New York

Iodine Uptake and Loss - Can Frequent Strenuous Exercise Induce Iodine Deficiency?

P.  P.  A.  Smyth1 , L.  H.  Duntas2
  • 1Endocrine Laboratory, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Ireland
  • 2Endocrine Unit, Evgenidion Hospital, University of Athens, Greece
Further Information

Publication History

Received 14 February 2005

Accepted after Revision 6 June 2005

Publication Date:
20 September 2005 (online)


Most of the daily dietary iodine intake (approximately 90 %) will be excreted in the urine; measurement of urinary iodine excretion is thus routinely used as an index of dietary iodine intake. However, urinary excretion is not the only means of iodine loss. Subjects such as athletes or those participating in vigorous exercise can lose a considerable amount of iodine in sweat, depending on environmental factors such as temperature and humidity. In areas of lower to moderate dietary iodine intake, loss in sweat can equal that in urine. Although electrolyte loss in sweat is well-recognized and replacement strategies are adopted, there is less recognition of potential iodine loss. Crude calculations reveal that if sweat iodide losses are not replaced, dietary stores could be depleted in an athlete undergoing a regular training regime. The significance of these losses could be increased in areas where dietary iodine intake is lower in the summer months. Although there is little doubt that excessive sweating can induce a relative iodine deficiency state, there is no case as yet for iodine supplementation in those that take vigorous exercise. However, sustained iodine loss may have implications for thyroid status and possibly consequences for athletic performance.


  • 1 De Groot L J, Niepomniszcze H. Biosynthesis of Thyroid Hormone: Basic and Clinical Aspects.  Metabolism. 1977;  26 665-718
  • 2 WHO .Assessment of Iodine Deficiency Disorders and Monitoring their Elimination. WHO/NHD/01. 1 2001
  • 3 Delange F, de Benoist B, Pretell E, Dunn J T. Iodine deficiency in the world: Where do we stand at the turn of the century?.  Thyroid. 2001;  11 437-447
  • 4 Vought R L, London W T, Brown F A, Murphy R S, Eckloff J C. Iodine Intake + Excretion in Healthy Nonhospitalized Subjects.  American Journal of Clinical Nutrition. 1964;  15 124-132
  • 5 Carrasco N. Iodide Transport in the Thyroid-Gland.  Biochimica et Biophysica Acta. 1993;  1154 65-82
  • 6 Smyth P P, Dwyer R M. The sodium iodide symporter and thyroid disease.  Clin Endocrinol (Oxf). 2002;  56 427-429
  • 7 Spitzweg C, Morris J C. The sodium iodide symporter: its pathophysiological and therapeutic implications.  Clin Endocrinol (Oxf). 2002;  57 559-574
  • 8 Spitzweg C, Dutton C M, Castro M R, Bergert E R, Goellner J R, Heufelder A E. et al . Expression of the sodium iodide symporter in human kidney.  Kidney Int. 2001;  59 1013-1023
  • 9 Moody K D, Miller K L, White W J, Hurst W J, Lang C M. The Effects of Topical Povidone-I Solution on Serum Iodide Levels and Thyroid Uptake of I-131 in Dogs.  Health Physics. 1988;  55 9-13
  • 10 Stanbury J B, Ermans A E, Boudoux P, Todd G, Oken E, Tonglet R, Vidor G, Braverman L E, Medeiros-Neto G. Iodine-induced hyperthyroidism: occurrence and epidemiology.  Thyroid. 1998;  8 83-100
  • 11 Ajjan R A, Kamaruddin N A, Crisp M, Watson P F, Ludgate M, Weetman A P. Regulation and tissue distribution of the human sodium iodide symporter gene.  Clin Endocrinol (Oxf). 1998;  49 517-523
  • 12 Vayre L, Sabourin J C, Caillou B, Ducreux M, Schlumberger M, Bidart J M. Immunohistochemical analysis of Na+/I- symporter distribution in human extra-thyroidal tissues.  Eur J Endocrinol. 1999;  141 382-386
  • 13 Slominski A, Wortsman J, Kohn L, Ain K B, Venkataraman G M, Pisarchik A. et al . Expression of hypothalamic-pituitary-thyroid axis related genes in the human skin.  J Invest Dermatol. 2002;  119 1449-1455
  • 14 Bricker N S, Hlad C J. Observations on the mechanism of the renal clearance of 131 I.  J Clin Invest. 1955;  34 1057-1072
  • 15 Wapnir I L, van de Rijn M, Nowels K, Amenta P S, Walton K, Montgomery K. et al . Immunohistochemical profile of the sodium/iodide symporter in thyroid, breast, and other carcinomas using high density tissue microarrays and conventional sections.  J Clin Endocrinol Metab. 2003;  88 1880-1888
  • 16 Mao I F, Chen M L, Ko Y C. Electrolyte loss in sweat and iodine deficiency in a hot environment.  Archives of Environmental Health. 2001;  56 271-277
  • 17 Maughan R J, Merson S J, Broad N P, Shirreffs S M. Fluid and electrolyte intake and loss in elite soccer players during training.  International Journal of Sport Nutrition and Exercise Metabolism. 2004;  14 333-346
  • 18 Suzuki M, Tamura T. Iodine Intake of Japanese Male University-Students - Urinary Iodine Excretion of Sedentary and Physically Active Students and Sweat Iodine Excretion During Exercise.  Journal of Nutritional Science and Vitaminology. 1985;  31 409-415
  • 19 Mao I F, Ko Y C, Chen M L. The Stability of Iodine in Human Sweat.  Japanese Journal of Physiology. 1990;  40 693-700
  • 20 Vanderpump M P, Tunbridge W M. Epidemiology and prevention of clinical and subclinical hypothyroidism.  Thyroid. 2002;  12 839-847
  • 21 Maresh C M, Gabaree-Boulant C L, Armstrong L E, Judelson D A, Hoffman J R, Castellani J W. et al . Effect of hydration status on thirst, drinking, and related hormonal responses during low-intensity exercise in the heat.  J Appl Physiol. 2004;  97 39-44
  • 22 Phillips D IW, Nelson M, Barker D JP, Morris J A, Wood T J. Iodine in Milk and the Incidence of Thyrotoxicosis in England.  Clinical Endocrinology. 1988;  28 61-66
  • 23 Hetherton A M, Smith D F, Gutekunst R, Smyth P PA. Do Variations in dietary intake contribute to the iodine status of a population without endemic goitre?.  Experimental and Clinical Endocrinology. 2005;  97 371
  • 24 Glinoer D. The regulation of thyroid function in pregnancy: pathways of endocrine adaptation from physiology to pathology.  Endocr Rev. 1997;  18 404-433
  • 25 Smyth P P, Hetherton A M, Smith D F, Radcliff M, O'Herlihy C. Maternal iodine status and thyroid volume during pregnancy: correlation with neonatal iodine intake.  J Clin Endocrinol Metab. 1997;  82 2840-2843
  • 26 Delange F. Optimal Iodine Nutrition during Pregnancy, Lactation and the Neonatal Period.  Int J Endocrinol Metab. 2005;  2 1-12
  • 27 Smyth P P. Variation in iodine handling during normal pregnancy.  Thyroid. 1999;  9 637-642

Peter P. A. Smyth M.Sc., Ph.D.

Endocrine Laboratory, Dept Medicine and Therapeutics ·

Conway Institute of Biomolecular and Biomedical Research · UCD · Belfield · Dublin 4 · Republic of Ireland ·

Phone: +353 (1) 716 67 36

Fax: +353 (1) 716 67 01

Email: ppa.smyth@ucd.ie