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10 Cards in this Set

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What are the diseases of Iodine deficiency?
Goiter (adults)
Cretinism
Describe Goiter
Enlargement of the thyroid gland
Impaired mental function, apathy
Describe cretinism
Two forms:
1. Neurological: blind/deaf/mute; squinty; metally retarded
2. Myxedematous: dwarfsism, metally retarded, motor spasticity
When do you get neurological form vs. myxedemitous?
Neurological: in womb and neonatal

Myxedemitous: throughout life
Absorption/transport/excretion of I?
Absorpted well, throughout GI tract - as iodide
Transport in free form in plasma
Excreted in urine
Iodide Metabolism in thyroid
1. Active uptake w/Na,K-ATPase
2. Rxn w/H2O2 to activate. enzyme = thyroid hydroperoxidase
3. Tyrosyl residues in thryroglobulin iodinated to form MIT and DIT-thyroglobulin
4. These combine and form T3 and T4-thyroglobulin. This all occurs in follicular space.
5. Stimulates pinocytosis of compound; combines w/lysosomes which degrade thyroglobulin.
6. T3 and T4 release via microtubules into circulation
Mechanism of action of T3
It's a sterioid-like hormone like A, D. In target tissues, it binds with nuclear receptors (RXR, TR) which interact w/DNA and modulate transcription.
How does T3 affect bone?
In kids, stimulates osteoblasts. Builds bones. When deficienct, retarded growth and delayed bone age.
How does T3 affect neural tissue?
During fetal development:
Nueral cell mitosis and differentiation impaired. Failure to develop visual/audio regions of cerebral cortex.

IQ is low.
What are goitrogens?
Compounds contained within certain foods that accentuate iodine deficiency:
Cassava: cyanogens. form thiocyanate and prevent iodide uptake into thyroid.

Other foods - millet, sweet potato.. do not CAUSE deficiency if intake sufficient.