IODINE METABOLISM
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Iodine Metabolism
Gandham. Rajeev
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The total body contains about 20 mg of iodine.
80% is present in the thyroid gland.
Muscles, salivary glands & ovaries also
contain some amount of iodine.
Sources:
Rich sources of iodine are sea foods, eggs,
dairy products, vegetables & iodized salts.
RDA:
150 - 200 µg/day
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Metabolism
Iodine is absorbed from upper small intestine.
Iodine is transported in plasma by loosely
binding to plasma proteins.
Iodine absorption also occurs through skin &
lungs.
80% of body’s iodine is stored in the organic
form as iodothyroglobulin in thyroid gland.
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Iodothyroglobulin contains thyroxine,
diiodotyrosine, & triiodothyronine.
About 2/3rd of iodine is excreted through urine.
Also excreted through bile, skin & saliva.
Plasma iodine: 4 – 10 mg/dl.
Most of this is present as protein bound iodine
(PBI).
It represents the iodine levels.
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Functions
The most important function of iodine in the
body is in the synthesis of thyroid hormones,
triiodothyronine (T3) and tetraiodothyronine
(T4), which influence large number of
metabolic functions.
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Disease states
Causes of iodine deficiency
Dietary deficiency & ingestion of goitrogens in
the diet.
A deficiency of iodine in children leads to
cretinism and in adults goitre.
The most common cause is dietary deficiency
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Goiter
Abnormal increase in the size of the thyroid
gland is known as goiter.
Decreased synthesis of thyroid hormones & is
associated with elevated TSH.
Goiter is primarily due to a failure in the auto
regulation of T3 & T4 synthesis.
This may be caused by deficiency or excess of
iodide
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Goitrogenic substances (goitrogens)
These are the substances that interfere with
the production of thyroid hormones.
Include thiocyanates, nitrates & perchlorates.
Drugs such as thiourea, thiouracil,
thiocarbamide etc.
Plant foods - cabbage, cauliflower contain
goitrogenic factors (mostly thiocyanates)
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Simple endemic goiter
Due to iodine deficiency in the diet.
Mostly found in the geographical regions,
where the water & soil are low in iodine.
Consumption of iodized salt is advocated to
overcome the problem of endemic goiter.
In certain cases, administration of thyroid
hormone is also employed.
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Hypothyroidism in children is associated with
physical & mental retardation, known as
critinism.
Critinism
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Thank you