The document summarizes iodine metabolism. It states that iodine is primarily stored in the thyroid gland where it is used to synthesize the thyroid hormones triiodothyronine and tetraiodothyronine. Dietary sources of iodine include seafood, eggs, dairy, and iodized salt. A deficiency of iodine can lead to goiter or cretinism in children, while excess iodine or goitrogenic substances can also interfere with thyroid hormone production.

1. Iodine Metabolism
Gandham. Rajeev

2.  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

3. 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.

4.  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.

5. 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.

6. 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

7. 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

8. 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)

9. 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.

11.  Hypothyroidism in children is associated with
physical & mental retardation, known as
critinism.
Critinism

12. Thank you