1pp HUN 4221 Iodine Lecture 11

1pp HUN 4221 Iodine Lecture 11 - Iodine di 2011 Iodine di...

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Iodine 011 2011
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Iodine 011 2011
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Iodine: Form • Iodine is typically found in its ionic form iodide (I - ) • Dietary iodine (I) is either bound to an amino acid or free as iodate (IO 3- ) or I - • In enterocyte, all iodine = iodide (I - )
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Iodine: Food Sources • Water – Concentration varies regionally – Fresh water: 0.5-2 ppb – Seawater: 17-50 ppb • Seafood i h h llfi h d – Fish, shellfish, seaweed
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Iodine: Food Sources • Meat and vegetable content varies depending on soil content of region where produced • Food processing – Iodides in bread production – Dairy industry in cleaners used for milking equipment
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Iodine: Regional Differences = areas of low soil/water iodine content
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Iodized Salt • Salt is the recommended vehicle for distributing iodine • Effective for >50 years in US, Canada, Switzerland • Iodine deficiency and goiter were once common
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Iodine: Absorption • Iodide rapidly and ~100% absorbed in stomach and small intestine • Iodate (IO 3- ) used in fortification – High bioavailability
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Test Question Iodine is a voluntary addition to “enriched” cereal grain products by the food industry in the US. ) True (a) True (b) False
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Test Question Iodine is a voluntary addition to “enriched” cereal grain products by the food industry in the US. ) True (a) True (b) False
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Transported as free iodide Fig. 12-18, p. 517
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Iodine: Transport • Rapidly taken up by thyroid gland or kidney • Thyroid uptake varies with iodine intake – Adequate intake, ~10% of absorbed iodine – Iodine deficiency, >80% may be taken up
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Test Question Iodine is transported in circulation bound to thyroglobulin. (a) True ) False (b) False
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Test Question Iodine is transported in circulation bound to thyroglobulin. (a) True ) alse (b) False
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Iodine: Excretion • Primary route of excretion is urinary – ~80-90% • Kidneys – no mechanism to conserve iodide • Low fecal excretion
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Iodine: Distribution and Storage • Total body – 15-20 mg iodide (adequate intake) – May be reduced to <20 μ g fi i ) (deficiency) •T h yroid gland yg – Contains 3/4 of total body iodide
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Iodine: Metabolism • Blood iodide concentration cleared pidly from plasma by thyroid gland rapidly from plasma by thyroid gland • The thyroid gland - not the intestinal tract or kidney controls the y concentration of blood iodide
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Test Question The primary regulation of blood iodine concentration is uptake by the thyroid gland. ) True (a) True (b) False
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Test Question The primary regulation of blood iodine concentration is uptake by the thyroid gland. ) rue (a) True (b) False
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Iodine: Function Iodide’s single function Synthesis of thyroid hormones by the thyroid gland Triiodothyronine (T3) Thyroxine (T4)
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Iodine: Thyroid Hormones
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Thyroid Hormone Synthesis: Step 1 •Thyroid cells trap dide via Na + + Na + iodide via Na /K ATPase pump Colloid K + I - •Iodide is oxidized to iodine I - Thyroid Cells
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Thyroid Hormone Synthesis: Step 2 •Iodine binds to tyrosyl sidues of olloid Thyroperoxidase hg IT residues of thyroglobulin (Thg) Colloid Thg-MIT •Thg-MIT is formed H 2 O + OH· I - •Hydrogen peroxide accepts electron H 2 O 2 Thyroid cell
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This note was uploaded on 12/09/2011 for the course HUN 4445 taught by Professor Sitren during the Spring '08 term at University of Florida.

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1pp HUN 4221 Iodine Lecture 11 - Iodine di 2011 Iodine di...

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