Iodine Flashcards
What is the primary biological function of iodine?
Synthesis of thyroid hormones (T3 & T4)
True or False: Iodine has multiple major functions in the human body.
False
- its major function is to synythesize thyroid hormones
What are the physiological effects of iodine deficiency?
Widespread effects, major global health issue
-deficiency leads to lack of thyroid hormones which can be a fatal deficiency
How does the iodine content in food vary? where is it primarily found?
Depends on soil iodine levels, geographic location and weathering
-Iodine is very soluble and is associated with run off and bodies of water
What factors influence iodine presence in soil?
- Runoff near water sources
- Weathering (rain, snow, glaciation)
Name three types of regions that tend to be iodine-deficient.
- Mountainous areas (Himalayas, Alps)
- Flood-prone regions (Ganges River)
- Landlocked areas with low seafood intake
What are the best natural sources of iodine?
- Seafood & seaweed
- Dairy products
- Eggs
What is the primary fortified source of iodine in many countries?
Iodized salt
-responsible for the near eradiaction of deficiency in countries that iodize their salt
What is the Recommended Dietary Allowance (RDA) for iodine in adults? what unit is this in?
150 µg/day
What is the RDA for iodine during pregnancy? what unit is this in?
220 µg/day
-needs almost double during pregnancy
How is iodine primarily absorbed in the body?
In the form of iodide (I⁻), rapidly absorbed in the small intestine
Where is the majority of iodine stored in the body? how much is stored in the body? what does this mean for deficiency?
~65% is stored in the thyroid gland
-15-20mg are stored in the thyroid, meaning symptoms of deficiency would take months to be seen
What is the main site of iodine excretion? How does the structure of iodine impact its excretion?
Kidneys
-due to its high solubility, larger amounts of iodine are seen in the filtrate
What is thyroglobulin (TG)?
A protein synthesized by follicular cells in the thyroid gland
-precursor to thyroid hormones
What forms are produced in thyroid hormone synthesis? what is the difference between these forms? when are each secreted? why?
- T3 (Triiodothyronine)
-active form - T4 (Thyroxine)
-inactive form
they are both secreted at the same time; secretion of the inactivate form along with the active form allows the body to regulate the synthesis of thyroid hormones by sending out an inactive form first as well
What converts T4 into T3 in peripheral tissues? what are the types? how do they differ?
Deiodinase enzymes
Type 1: liver, kidney, thyroid
Type 2: brain, adipose, pituitary
True or False: T4 is the active form of thyroid hormone.
False
-T4 is the inactive form
How are T3/T3 formed? what is it bound to
T3 = DIT + MIT + Thyrogobulin
T4 = DIT + DIT + Thyrogobulin
What physiological roles does T3 play?
- Regulates gene expression
- Mitochondrial protein synthesis
- Lipid metabolism
- Carbohydrate metabolism
- Protein metabolism
- Ion transport and muscle contraction
What are common causes of iodine deficiency?
- Low dietary intake
- High intake of goitrogens
- Increased iodine requirements
What are symptoms of iodine deficiency?
- Hypothyroidism
- Goiter
- Cretinism
How does Iodine deficiency cause goiter?
1) Low iodine
2) body can’t make T3/T4
3) TRH/TSH increased to stimulate thyroid hormone synthesis
4) enlargement of thyroid follicles
How can iodine supplementation protect against radioactive iodine exposure?
By saturating the thyroid with stable iodine
-supplemental iodine competes with radioactive isoform in order to saturate the thyroid with non radioactive isoforms
What is another use for iodine outside of the body?
Used as an anti septic
-pink eye drops
-Topical cream for foot sores
-Anti-bacterial surgical prep
-Reduces sores and swelling
