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21 Cards in this Set
- Front
- Back
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What is the active thyroid hormone?
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free T3
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Where in the cell does T3 act?
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Inside the nucleus: nuclear receptor proteins (often associated with the retinoic acid receptor)
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Where on the DNA does T3 generally act?
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Specific hormone-responsive elements in the 5' flaking region of target genes
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What are some receptor families related to the T3 receptors?
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Steroids
REtinoids Vitamin D |
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How do the T3 receptors bind to DNA?
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Heterodimers with retinoid X receptors
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What is more serious: missing the T3 receptor or T3 itself?
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T3 itself.
Unliganded T3 receptors aren't neutral in themselves; they repress genes activated by T3, activate genes repressed by T3. So, without T3, you still have some sort of biologic activity, which explains why not having T3 is worse. |
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What's the relationship between T3 and growth hormone?
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Hypothyroid people have low growth hormone; don't grow as rapidly as others
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What are some common labs that we order to look at thyroid function?
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Serum T4
Serum T3 TSH Anti-thyroid antibodies Thyroid uptake and scan |
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What do we want to measure when we're looking at T4?
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Free t4: it's the only thing that's biologically active
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What is the effect of hyperthyroidism on T4? Hypothyroidism? T3?
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Hyperthyroidism: high T4, T3
Hypothyroidism: low T4, T3 |
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What is the effect of primary hyperthyroidism on TSH levels?
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Lowers levels
If the problem isn't at the thyroid, then you won't have a low TSH |
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What is the effect of primary hypothyroidism on TSH levels?
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It goes up!
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What's the best screening test for hyperthyroidism and primary hypothyroidism?
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TSH
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What are some antibodies that you should look for in thyroid pathology?
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Antithyroid antibodies: hashimoto's, graves
Anti-TPO (microsomal): hashimoto's |
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What's the most common cause of hypothyroidism?
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Hashimoto's
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What's the most common cause of thyroid disease?
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Antithyroglobulin antibodies
90% of hashimoto's 60% of graves' patients |
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What test can you do to evaluate causes of hyperthyroidism?
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Radioiodine uptake
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What's the interpretation of a radioiopdine uptake test?
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High: hyperfunctioning thyroid gland
Low: thyroid hormone is leaking (thyroiditis); patient is taking excess exogenous thyroid hormone |
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When you take a scan of the thyroid gland, what is the most worrisome kind of nodule?
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Cold: no uptake of the tracer.
These are sometimes malignant! |
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What happens in a "hot" thyroid nodule?
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Too much uptake of the tracer in one location
You don't see the regular architecture of the gland. These aren't usually malignant |
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What does a goiterous thyroid look like in a scan?
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Multinodular
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