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NFS382 > Iodine > Flashcards

Iodine Flashcards

1
Q

How much iodine does human body contains?

A

ultra-trace element (mineral NOT metal)
-contains 15-20 mg

70-80% found in thyroid
iodine (I-) form (anion)

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2
Q

Iodine RDA?

A

we cannot always say this food will have this many iodine because highly variable based on how much iodine from soil and food processing

human needs iodine (not vary hugely)

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3
Q

What are some sources of iodine?

A

food content variable based on soil and type of fertilizer used

  • foods of ocean origin (vs. fresh water) contain higher levels of iodine
    ex. seaweed, fish
  • Dairy products contain iodine via additives added to animal feed and use of iodine-containing disinfectants on cows, milking machines and storage containers (not always in there)
  • iodized salt
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4
Q

How is iodine absorbed in the body?

A

Bound to amino acids in food
–>freed via digestion

in food as: free iodine (I-) or iodate (IO3-)

  • absorb completely and rapidly from stomach (lesser in duodenum) >90%
  • travels as free iodine in blood
  • concentrates in thyroid gland by Na/I transporter (20x-50x conc. of plasma)
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5
Q

Where is iodine mainly absorbed?

A

stomach

>90% absorbed

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6
Q

What is the form that iodine travel in blood?

A

free iodine

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7
Q

What is the main function of iodine?

A

Synthesis of thyroid hormones:

  • Thyroxine (T4) and Triiodothyronine (T3)
  • T4 & T3 occupy on nuclear receptors–> gene expression
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8
Q

How is thyroid function regulated?

A

primarily regulated by thyroid-stimulating hormone (TSH)
TSH secreted by pituitary gland to control TH production and secretion
–>protecting body from hypothyroidism and hyperthyroidism

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9
Q

How is thyroid hormones transported in blood?

A

Protein bound:
thyroxine-binding globulin, albumin, transthyretin (prealbumin)

<0.1% not bound to a binding protein

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10
Q

What is the role of thyroid hormones in gene expression?

A

turn ON transcription of gene
-plasma protein w/ T4 and T3 travel to target cells these proteins

50x more T4 made than T3 –> bind to receptor on cell–> facilitated diffusion–> T4 converted to T3 (bioactive) in cells –>goes into nucleus and binds to nuclear protein receptor –> complex goes to regulatory region of gene

  • ->promote transcription
  • ->translation of new proteins
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11
Q

What is the role of thyroid hormones in gene expression?

A
  1. TH (T3, T4) circulate in blood bound to plasma proteins
  2. T4 and T3 enter cell where selenium-containing enzyme converts T4 –> T3
  3. T3 enters nucleus and binds to nuclear protein receptor
  4. T3-protein receptor complex binds to regulatory region of target gene
  5. Transcription of genes turned on–> increasing amount of mRNA made
  6. mRNA directs translation–> increasing synthesis of protein coded by target gene
  7. increase in the amount of protein–> cellular functions and body processes affected by this protein
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12
Q

What are some physiologic effects of thyroid hormones?

A

Adipose tissue: enhance lipolysis

Muscle: enhance contraction

Bone: promotes anabolism (growth and development)

CVS: increase heart rate

GI tract: stimulates nutrient digestion and absorption

Metabolism: stimulates metabolic rate and cellular oxygen consumption in metabolically active tissues (ex. muscle)

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13
Q

What are some interactions of iodine with other nutrients?

A

Impaired selenium status–> affects TH metabolism (via selenium-dependent iodothyronin-5’-deiodinases)

Iron, vit.A deficiencies may worsen effects of deficiency

  • heme iron involved in TH synthesis (maybe attaching T3 to nuclear receptor)
  • vit.A deficiency appears to reduce (not inhibiting) iodine uptake at thyroid gland and syn. of TH

Goitrogens interfere w/ iodine metabolism
-found in turnips, rutabaga, cabbage, cassava, and millet
-cooking reduces and not likely used enough to impact status in Ca.
-Cassava used as a dietary staple in some parts of the world
(Goitrogens: substance that affects iodine metabolism)

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14
Q

How is iodine being excreted?

A

Most in urine (kidneys dont have mech. to conserve)

  • kidneys does not reabsorb
  • feces (low)

-Sweat: potentially a problem in tropics (intake inadequate)

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15
Q

What are some factors affecting iodine RDA?

A

Geographical, ethnicity, cultural, religious reasons
iodine salts

biggest health concern: sodium
ex. hypertension patient can also be reducing iodine intake
-most salt in diet comes from processed package food (salt not iodized)
only salt for home use and store has to be iodized

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16
Q

What are some effects of iodine deficiency?

A

Reduces production of TH
-metabolic rate slows, weight gain (?)

Iodine deficiency and iodine deficiency disorders (IDD)
-Goiter (enlargement of thyroid in response to increased production of TSH)
-Cretinism: nuerological or hypothyroid
(deficient preg. women passed down to offspring)
-iodized salt, oil used for treatment

17
Q

What is Goiter? (Iodine deficiency and iodine deficiency disorders (IDD))

A

enlargement or hyperplasia of the thyroid gland due to overstimulation by TSH

not permanent, reversible (several months-years)

18
Q

What is Cretinism?

Iodine deficiency and iodine deficiency disorders (IDD)

A

iodine deficiency in fetus–> ID from mother

nuerological manifestations: cognitive, language, motor impairment

permanent, irreversible
iodine supp. may help mitigate

19
Q

What is the toxicity of iodine?

A

UL = 1,100 microgram

based on thyroid dysfunction (elevated serum TSH)

20
Q

How do we assess iodine status?

A

Urinary iodine excretion (recent dietary intake)
-due to variability–require duplicate measures

Thyroid size

Serum thyroid-stimulating hormone (TSH) conc.

21
Q

WHO urinary iodine concentration recommended for nutritional sufficiency

A

<0.16 severe deficiency

> 2.37 excessive intake

22
Q

What is the prevalence of iodine inadequacy?

A

mild iodine deficiency (3-79 yrs): just under 25%
-potential problem

UIC in non-preg. non-lac. women:
consume most dairy–>highest iodine level
No dairy–> marginally inadequate
–potential problem: babies may be endanger w/ hypothyroidism

23
Q

is sea salt, which has not been iodized, a permitted ingredient of a food?

A

YES
sea salt which has not been iodized is permitted as an ingredient of a food
only salt for table or general household use to be iodized

-when salt/sea salt is sold for table/general household use–> must be iodized

more than 70 countries add iodine to salt
29-50% world’s pop. deficient
-mountain areas: most iodine -deficient

NFS382 (15 decks)

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