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USMLE Step 1 Bits & Pieces High yield short focused bulleted points, monographs, charts, illustrations, and USMLE Step 1 oriented materials

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Old 12-04-2009
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Glands Radioactive Iodine Uptake in Thyroid diseases

It's wise to remember that not all cases of hypothyroidism are associated with decreased Iodine uptake and not all cases of hyperthyroidism are associated with increased Iodine uptake.

Examples of hyperthyroidism with increased uptake:
  • Typically Grave's disease as the autoantibodies stimulate TSH receptor sensitivity enhancing the uptake.
  • Secondary and tertiary hyperthyoroidism where the elevated TSH levels also stimulate the uptake.
  • Toxic adenoma in which the overactive adenoma need to take Iodine to support the production of T4.
Example of hyperthyroidism with decreased uptake:
  • Factitious hyperthyroidism in which the exogenous T4 causes feedback inhibition on the TSH secretion.
  • Any other exogenous thyroxine sources such as struma ovarii.
  • Iodine induced thyroid toxicosis.
  • Release of thyroid hormone by destructive process e.g. temporary hyperthyroidism seen in subacute thyroiditis.
  • Toxic Nodular Adenoma, the nodule is active (causing hyperthyroidism) but the rest of the gland is with decreased uptake due to suppressed TSH.
Example of hypothyroidism with increased uptake:
  • Thyroid hormone receptor insensitivity in which the T4 has no peripheral effects (hence the hypothyroidism) and no feedback effects (hence the elevated TSH and increased uptake).
Example of hypothyroidism with decreased uptake:
  • Hashimoto, De Quervain, and Reidle thyroditis are all associated with decreased Iodine uptake.

Thyroid carcinoma may variable be hyperthyroid/hypothyroid and Cold/Hot on radioactive Iodine uptake tests.

Last edited by rasheed; 02-07-2010 at 02:08 PM.
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The Following 6 Users Say Thank You to rasheed For This Useful Post:
aungawa (04-30-2010), fin-84 (3 Weeks Ago), janyloo (04-29-2010), Seetal (04-29-2010), wahaha007 (01-10-2010), Zagaris (07-16-2010)



Old 07-16-2010
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Thumbs Up Nice

That's wonderful.

Thank you very much
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Old 07-22-2010
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thnx a lot , really its a valuable info......
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Old 07-22-2010
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Smile thank you rasheed, for nice information.you such help increse our knowledge day by day.

Thank you rasheed for nice information.
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