Term
| Where are thyroid hormone receptors located? |
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Definition
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Term
| Where are thyroid hormone receptors located? |
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Definition
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Term
| What are the overall effects on the body of thyroid hormones? |
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Definition
1. Promote bone growth
2. Promote brain development
3. Stimulate metabolism
4. Enhance autonomic reflexes |
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Term
| What are the effects of thyroid hormones on metabolism? |
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Definition
1. Increased protein synthesis and degradation (leads to increased O2 consumption)
2. Increase Na/K ATPase (increases basal metabolic rate)
3. Increases Uncoupling protein (generates heat) |
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Term
| What three tissues do not increase O2 consumption in response to thyroid hormone? |
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Definition
| Brain, spleen, and testis |
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Term
| How do thyroid hormones increase the basal metabolic rate? |
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Definition
1. Increase body temperature
2. Increase Na/K ATPase |
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Term
| What 2 methods does thyroid hormone have for feedback inhibition? |
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Definition
1. Thyroid hormones inhibit synthesis of thyroid stimulating hormone
2. Thyroid hormones decrease thyroid releasing hormone receptor density |
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Term
| Hormones that signal the thyroid gland originate in what part of the pituitary gland? |
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Definition
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Term
| What ion is necessary for the synthesis of Thyroid hormones? |
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Definition
Iodide (can also be taken up as Iodate)
Note: Deficiency of iodine is the leading preventable cause of mental retardation |
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Term
| What 2 enzymes are involved in the synthesis of T3 and T4 and what do they do? |
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Definition
1. Thyroid oxidase - makes H2O2 from O2
2. Thyroperoxidase - uses H2O2 to activate iodide to allow iodination reactions to occur |
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Term
| When thyroid stimulating hormone triggers the release of T3 and T4, how much of each is released relative to each other? |
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Definition
| About 10x more T4 is released then T3 |
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Term
| What enzymes activity triggers the release of thyroid stimulating hormone from the pituitary in response to the presence of thyroid releasing hormone? |
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Definition
| Phospholipase activity (its activity causes increased Ca levels in the cytoplasm, promoting vesicle fusion with the membrane) |
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Term
| What is the main source of iodide in thyroid hormone production? |
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Definition
Dehalogenase enzyme that breaks down left over MIT and DIT during T3 and T4 release.
This supplies about twice as much as the Na-I exchanger |
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Term
| What are the 3 thyroid hormone carriers in the blood? Which one has the highest affinity for the thyroid hormones? |
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Definition
1. Thyroid binding globulin
2. Transthyretin
3. Albumin |
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Term
| Of the 2 thyroid hormones, which one has the longer half life in blood?? |
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Definition
| T4 (about 8 days) is longer then T3 which is about 1 day |
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