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.


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