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15 Cards in this Set
- Front
- Back
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(T/F) A normal radioidone uptake alone cannot be used to exclude the diagnosis of hyperthyroidism when it is clinically suspected.
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True.
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Why has it become increasingly difficult to use reduced radioiodine uptake as an indicator of hypothyroidism?
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Because of the prevalence of iodine in the American diet.
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Which substance reflects both trapping and organification in the gland? I-123 or Tm99
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I-123.
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If you're looking for ectopic thyroid tissue, what study to do?
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24 hour imaging with I-131
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In congenital organification defect, what is seen on a 24 hour radioiodine scan?
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No activity in thyroid because without organification, trapped iodine washes out of gland
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In congenital organification defect, what do you see on a 99mTc or 2-4 hours I-123 scan?
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Presence of thyroid gland because trapping mechanism is intact.
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75% of nonfunctioning thyroid nodules are due to ?
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Colloid cyst or adenoma
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20% of solitary cold nodules are?
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carcinomas
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Hot nodules almost always represent?
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Hyperfunctioning adenomas, of which up to half are autonomous
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Solitary hot nodule on pertechnetate scan + cold nodule on 24 hour radioiodine scan refers to ___?
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Discordant nodule
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Two main reasons for discordant nodule?
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Lack of organification of iodine within the nodules or rapid turnover of organified iodine within the nodules.
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Many warm nodules are actually?
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Cold nodules deep within the thyroid gland with overlying normally functioning tissue
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What is stunning?
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Reduction in transport of radioiodine into cells due to beta radiation from dignostic dose from whole body radioiodine imaging using I131 after thyroidectomy for detection of residual thyroid tissue or functioning mets.
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When follow up I131 imaging is performed, patients should undergo thyroid hormone withdrawal for how long?
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4-6 weeks to allow endogenous serum TSH levels to rise so that stimulation of any residual normal thyroid tissie or functioning mets can enhance likelihood of detection
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If you don't want to do thyroid hormone withdrawl, you can give ---?
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recombinant human thyrotropin ie Thyrogen or rhTSH
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