In peripheral tissues, the enzyme 5'-deiodinase is responsible for which critical step in thyroid hormone metabolism?
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Correct answer: Converting T4 into the more potent T3
T4 is considered a pro-hormone with relatively low activity. 5'-deiodinase removes an iodine atom from the outer ring of T4 to create T3, which has a much higher affinity for nuclear thyroid receptors.
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