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The Seaweed Gatherers, Paul Gaugin
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Resource Network of The Iodine Movement
Iodine and the Body
Iodine is an essential nutrient primarily because of its role as an indispensable component of the
thyroid hormones T3 and T4. The thyroid hormones are the only iodine-containing hormones in
vertebrates. Without iodine there is no biosynthesis of thyroid hormones. Therefore, thyroid
function ultimately depends on an adequate supply of iodine to the gland.
A remarkably efficient and specialized system has evolved in the thyroid that ensures that most
of the ingested dietary I- (the only source of I-) is accumulated in the gland and thus made
available for T3 and T4 biosynthesis.
The significance of this becomes more apparent when one considers that I- is rather scarce in
In addition to this essential role in thyroid hormone formation, iodine also influences a wide
variety of specific functions in the thyroid, affecting many chemical processes and even the size
of the thyroid.
What are the major hormones produced by the thyroid? Why are they important? How much
iodide do they contain? How do they get from the thyroid to the cells? What affects the thyroid
hormone receptors? How does T4 get transformed into T3? How do extra-thyroidal processes
control hormone levels in the cells? What do the hormones do in the cells?
How does iodide get into the thyroid cell? What is the NIS symporter? How does it function, and
what controls it? Where is it found besides the thyroid? What are the iodine/iodide transporters
besides the NIS?
Thyroid Hormone Synthesis
How is the iodide turned into hormones? What components besides iodide are necessary for this
process? What happens to the hormones once they are created?
How does the thyroid adapt to changing conditions so that it can provide the hormones that are
needed? What is TSH and why is it important? How does the thyroid use iodide in its own
Effects of Iodine Deficiency
What are the effects of iodine deficiency on the thyroid? What happens to the T4, T3, and TSH
when there is not very much iodine? How does the thyroid adapt to conditions of iodine
deficiency? How much iodine is necessary?
Effects of Iodine Excess
What are the effects of iodine excess on the thyroid? What happens to the T4, T3, and TSH
when there is lots of iodine? How does the thyroid adapt to conditions of iodine excess? How
much iodine is too much?
How much iodine is in the thyroid?
How do the above principles of thyroid physiology relate to some common thyroid problems:
hypothyroidism, hyperthyroidism, goiter, autoimmune issues, and cancer? What is the role of
iodine in each of these?