Thyroid Dysfunction Flashcards

1
Q

Which deiodinase deactivates T4?

A

Type 3 deiodinase (which creates reverse T3)

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2
Q

What can promote a shift to type 3 deiodinase?

A
Starvation
Severe illness
Neonatal period
Stress
Glucocorticoids
Propranolol
Amiodarone
Radiocontrast dyes
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3
Q

What percent of T4 is free?

A

0.02%

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4
Q

Decreased thyroid binding proteins can cause ___________.

A

hypothyroidism

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5
Q

The normal range of TSH is _____________.

A

0.4 - 4.0 (treat if greater than 10)

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6
Q

What is the best test for thyroid dysfunction?

A

TSH (provided the pituitary does not show other signs of dysfunction)

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7
Q

_______________ leads to an increased expression of NIS.

A

TSH (NIS is Na-Iodide Symporter)

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8
Q

Thyrotoxicosis presents with _________________.

A

low TSH and high T3/T4

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9
Q

If TSH is low but the thyroid is still taking up iodide, then this is ________________.

A

true hyperthyroidism, characterized by the autonomous production of thyroid hormone

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10
Q

Deposition of hyaluronic acid in the anterior calves leads is called ____________ and is pathognomonic for Graves’ disease.

A

pretibial myxedema

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11
Q

The activating deiodinases are _________.

A

types I and II

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12
Q

What lab pattern is suggestive of subclinical hyperthyroidism?

A

Low TSH
Normal T4
Normal T3

(Similarly, subclinical hypothyroidism presents with elevated TSH but normal T4 and T3.)

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13
Q

Which cell type mediates the damage in Hashimoto’s?

A

Lymphocytes

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14
Q

Iodine uptake will be low in which types of hyperthyroidism?

A
  • Factitious
  • Struma ovarii
  • All the disorders that damage the thyroid (viral, onset of Hashimoto’s, autoimmune)
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