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10 Cards in this Set
- Front
- Back
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What are the diseases of Iodine deficiency?
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Goiter (adults)
Cretinism |
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Describe Goiter
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Enlargement of the thyroid gland
Impaired mental function, apathy |
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Describe cretinism
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Two forms:
1. Neurological: blind/deaf/mute; squinty; metally retarded 2. Myxedematous: dwarfsism, metally retarded, motor spasticity |
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When do you get neurological form vs. myxedemitous?
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Neurological: in womb and neonatal
Myxedemitous: throughout life |
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Absorption/transport/excretion of I?
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Absorpted well, throughout GI tract - as iodide
Transport in free form in plasma Excreted in urine |
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Iodide Metabolism in thyroid
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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 |
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Mechanism of action of T3
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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.
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How does T3 affect bone?
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In kids, stimulates osteoblasts. Builds bones. When deficienct, retarded growth and delayed bone age.
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How does T3 affect neural tissue?
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During fetal development:
Nueral cell mitosis and differentiation impaired. Failure to develop visual/audio regions of cerebral cortex. IQ is low. |
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What are goitrogens?
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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. |
