Iodine Flashcards
Iodine exists naturally as what?
I2 as a gas
What is Iodide?
The ionic form and is soluble in water
What foods is generally found in?
Variety but found in milk because Iodine is used as a disinfectant for milking supplies
Meat and vegetable content varies depending on?
Soil content of region where produced
What areas of the world are low in iodine?
Mountanous areas
What is the recommended vehicle for distributing iodine?
Salt
How is Iodide absorbed into the intestinal cell?
Via a Na/I symporter
What form of Iodide is used in fortification and why?
Iodate (IO3-) because it is highly bioavailable.
Iodide is taken up rapidly by what?
Thyroid glands and kidneys
When does the thyroid gland take up more or less Iodide?
More- in iodide def
Less- in adequate iodide intake
Primary route of excretion?
Urinary
Is there a mechanism to conserve iodide in the kidneys?
No
Where is most of the iodide in the body?
In the thyroid glands
What controls the concentration of blood iodide?
The thyroid gland only. not the intestinal tract not the kidney
What is Iodide’s function?
Synthesis of thyroid hormones by the thyroid gland
Which thyroid hormones are synthesized by Iodide?
Thyroxine (T4) and Triiodothyronine (T3)
Slide 19
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T4 and T3 are associated with 3 transport proteins:
Thyroxine-binding protein
- Albumin
- transthyretin
In order for T3 or T4 to be hormonally active it must be:
in the free form
Slide 21.
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Deiodination of T4 can produce
T3 or rT3
In order to deiondinate T4 what is needed?
5’-deiodinase
Status assessment of Iodine
Urinary iodine excretion and functional indicators such as Thyroxine (T4) or serum thyroid stimulating hormone (TSH)
What is the function of the thyroid hormones?
Regulator of prenatal cell growth
- influences neuronal health
- growth and maturation of peripheral tissues
- -deficiency causes delay in bone bone development
Thyroid hormone deficiency
Basal metabolic rate (BMR) decreased
Macronutrient metabolism impaired
Developmental abnormalities in the bran, muscle/skeletal/lung
Slide 27.
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Consequences of Iodine def?
Mental retardation Postnatally -delayed growth -slowness of movement -delayed reflexes -elevated blood lipids -cardiac insufficiency Goiter
What is the most common consequence of iodine def that can be prevented?
mental retardation
What is the compensatory response of Goiter?
Decrease Plasma iodide Hormone Synthesis Increase TSH release -Thyroid cell number increase -Thyroid cell size increase -Enlarged thyroid gland (goiter)
If function is gained back during goiter, it may lead to what?
Thyroxicosis- overproduction of hormone
What are symptomes of goiter?
Tracheal and esophagus pressure
May damage laryngeal nerves
respiratory difficulty
hoarseness
Your pituitary gland will sense what?
If your levels of T3 or T4 are low. If they are low, pituitary gland will make more TSH (thyroid stimulating hormone) to make more T3 or T4
How do you treat goiters if caught early enough?
Gradual reduction of thyriod gland size with iodine supplement OR thyroidectomy
What is the risk of having a thyroidectomy?
Patients may become hyperthyroid and require hormone replacement. Not practical in most affected places of the world.
In pregnancy, what happens to iodine excretion and thyroid hormone secretion?
Iodine excretion increases and thyroid hormone secretion increases
Decreased iodine during pregnancy may lead to?
Decreased thyroid hormone which leads to severe mental retardation and cretinism
What is cretinism?
Most severe form of damage from iodide deficiency
What is early pregnancy iodide deficiency?
Inner ear and brain affected
mental retardation
short stature but frewuently normal
What is late pregnancy iodide deficiency?
Known as myxedematous shorter stature mental retardation hypothyroidism spasticity of legs, deaf mutism, goiter usually absent
What are goitrogens?
Present in certain foods and blocks iodine uptake by thyroid (blocks Na/I symporter)
Selenium Def can cause what?
Iodine Def
How does Glutathione Peroxidase affect thyroid hormone synthesis?
It protects it from oxidative environment required for thyroid hormone synthesis.
What does T4 deiodinase do?
Converts T4 to T3
What happens to Iodine during selenium def?
Produces peroxidase deficiency in thyroid
deiododinase deficiency inhibits T3 production
