Iodine

Question 1

Major fxn

Answer 1

Master regulator of metabolism / syn of thyroid hormones

Question 2

What determines availability of Iodine in soils

Answer 2

Solubility in soil = different bioavailability
- Reduced in heavy floods
Location

Question 3

Best reliable source of Iodine

Answer 3

Food from the sea / salt (fortified)
Also in: meat, eggs, beef, bean, potato (60), bread, milk

Question 4

RDA for Iodine

Answer 4

Adults - 150 ug/day
Pregnant - 220ug/day
Lactating - 290ug/day

Question 5

How much is stored and where is iodine

Answer 5

15-20mg in body
65% stored in thyroid gland (rest in kidneys and other glands)
- Thyroid can concentrate iodine 100-fold more than plasma levels *

Question 6

Source of excretion?

Answer 6

Kidney - normal levels are 50 ug/g iodine

Question 7

Thyroglobulin

Answer 7

Precursors to thyroid hormones - iodine gets added through thyroid peroxidase; Synthesized in the follicular cells of thyroid gland follicles.

Question 8

DIT Vs. MIT

Answer 8

DIT - 2 iodine MIT - 1iodine
T4 - 2 DIT (turns process of)
T3 - 1 MIT + 1 DIT (Active)

Question 9

How do we activate T3

Answer 9

through deiodinase enzymes
Type 1: Liver, kidney, thyroid
Type 2: Brain, adipose, pituitary

Question 10

Thyroid Hormones and Synthesis

Answer 10

TSH in bloodstream
Activates cAMP - Protein K
Removes TG bound T3/4 from colloid
Lysosomes help move to blood stream through follicular cell
TG removed and recycled back into lumen for thyroid hormone synthesis
T3 binds nuclear receptors and activates syn of genes

Question 11

T3 regulates

Answer 11

Mitochondrial protein synthesis
Lipid metabolism
CHO metabolism
Protein metabolism
Ion transport
Muscle contraction.

Question 12

What is T4 responsible for

Answer 12

Neg feedback to hypothalamus + Ant Pit to cease TSH secretion and production of thyroid hormones.
Can also be converted to T3

Question 13

hypothyroidism

Answer 13

• Insufficient dietary iodine to synthesize T4
• Increases Thyroid stimulating hormone, causing enlargement of thyroid follicles and Goiter
• Can also be caused by excessive goitrogens: cabbage, spinach, radish, soybeans, peach, strawB

Question 14

Iodine supplementation for radiation exposure

Answer 14

Uranium-235 produces the reactive iodine-131, which is transmitted in the air and can cause cancer in the thyroid. Iodine supplementation can saturate the thyroid, preventing the absorption of the radioactive iodine-131.