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Iodine, Excessive Perspiration, and Athletic Performance. Patrick Kajeh Final Presentation July 2013. Thyroid Gland. Major endocrine gland, bi-lobed, located near the thyroid cartilage of the larynx Composed of two distinct cell types
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Iodine, Excessive Perspiration, and Athletic Performance Patrick Kajeh Final Presentation July 2013
Thyroid Gland • Major endocrine gland, bi-lobed, located near the thyroid cartilage of the larynx • Composed of two distinct cell types • Under the control of Hypothalamic-Pituitary-Thyroid Axis • Thyroid Hormones: T4 and T3
Thyroid Hormone Biosynthesis (Figure 1)
Effects of Thyroid Hormones • Effects on basal metabolic rate/heat production • Effects on intermediary metabolism (formation versus degradation of carbohydrates, fats, proteins, which is very dose dependant) • Sympatho-mimetic effects, especially in heart • Crucial effects on growth and CNS development
Iodine levels in the U.S.: • The National Health and Nutrition Examination Survey (NHANES) has been monitoring the general U.S. population’s iodine levels since 1971 • The general U.S. population is iodine sufficient. • Urinary iodine measurements, is a good indication and way of measuring individual’s iodine levels.
Food sources of iodine: • Dairy products and iodized salt are the main sources of iodine for the general population. • Iodine sources in dairy products are “partly due to the use of iodine feed supplements and iodophor sanitizing agents in the dairy industry” (1). (2)
Iodine deficiency in athletes: • Everyday, approximately 90% of dietary iodine intake will get excreted in the urine (3). • Excessive sweating in hot and humid environments can lead to more iodine loss (3). • Athletes are more prone to develop clinical symptoms of iodine deficiency (Goitre), due to excessive sweating and possibly poor diet.
Link between sweating in high intensity exercise and iodine deficiency: • A study was done in 2001 (4), that compared iodine levels of 13 soccer student athletes with 100 sedentary students. The results showed that soccer athletes were 38.5% more iodine deficient compared to 2% in the sedentary group (RDA levels of iodine for adults is 150 mcg, the soccer athletes lost an average of 52 mcg/hour exercise).
Conclusion • Iodine is a key factor in production of thyroid hormones. These hormones are significantly important in maintenance of energy. • Athletes lose more iodine compare to sedentary people because of sweating while performing in hot and humid environments. • Consequences of iodine deficiency are: fatigue, low energy, low stamina, and • Maybe poor athletic performance?!
References • Pennington JA, Young B. Iron, zinc, copper, manganese, selenium, and iodine in foods from the United States Total Diet Study. J Food Compost Anal. 1990 June;3(2):166-184. • "Iodine." — Health Professional Fact Sheet. National Institutes of Health, 24 June 2011. Web. 03 July 2013. <http://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/>. • Smyth PP, Duntas LH. Iodine uptake and loss-can frequent strenuous exercise induce iodine deficiency?. Horm Metab Res. 2005 Sep;37(9):555-8. • Mao IF, Chen ML, Ko YC. Electrolyte loss in sweat and iodine deficiency in a hot environment. Arch Environ Health. 2001 May-Jun;56(3):271-7.
Thyroid Hormone Biosynthesis: First, thyroglobulin protein (Tg) is synthesized in follicular cell and being secreted into colloid. Iodide will be transported from blood to the thyroid follicular cell through secondary active transporter in the basal side of the cell. Then iodide will be oxidized (activated) on the apical side of the cell by Thyroid peroxidase (TPO) enzyme and get transported into colloid. In the colloid, TPO adds one iodine to Tg to form MIT, or adds two iodine to Tg to form DIT. If one MIT and one DIT coupled together, a T3 molecule has been formed. If two DIT coupled together, a molecule of T4 forms. These T3 and T4 hormones are stored in the colloid till TSH stimulated their release. Then they will get transcytosed into the thyroid follicular cell by forming a vesicle. This vesicle in the cell will be fused with lysosome for digestion, therefore T3 and T4 will get separated and will go for secretion in to blood. The remaining DIT and MIT products of digestion will be recycled in the cell. (Figure 1)
THANK YOU Any Questions?