Thyroid Dysfunction Flashcards
Which deiodinase deactivates T4?
Type 3 deiodinase (which creates reverse T3)
What can promote a shift to type 3 deiodinase?
Starvation Severe illness Neonatal period Stress Glucocorticoids Propranolol Amiodarone Radiocontrast dyes
What percent of T4 is free?
0.02%
Decreased thyroid binding proteins can cause ___________.
hypothyroidism
The normal range of TSH is _____________.
0.4 - 4.0 (treat if greater than 10)
What is the best test for thyroid dysfunction?
TSH (provided the pituitary does not show other signs of dysfunction)
_______________ leads to an increased expression of NIS.
TSH (NIS is Na-Iodide Symporter)
Thyrotoxicosis presents with _________________.
low TSH and high T3/T4
If TSH is low but the thyroid is still taking up iodide, then this is ________________.
true hyperthyroidism, characterized by the autonomous production of thyroid hormone
Deposition of hyaluronic acid in the anterior calves leads is called ____________ and is pathognomonic for Graves’ disease.
pretibial myxedema
The activating deiodinases are _________.
types I and II
What lab pattern is suggestive of subclinical hyperthyroidism?
Low TSH
Normal T4
Normal T3
(Similarly, subclinical hypothyroidism presents with elevated TSH but normal T4 and T3.)
Which cell type mediates the damage in Hashimoto’s?
Lymphocytes
Iodine uptake will be low in which types of hyperthyroidism?
- Factitious
- Struma ovarii
- All the disorders that damage the thyroid (viral, onset of Hashimoto’s, autoimmune)