Reverse T3 (rT3) is typically elevated in patients with 'Sick Euthyroid Syndrome.' How is rT3 produced?
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Correct answer: By deiodination of T4 at the 5-position (inner ring)
rT3 is formed when T4 is deiodinated at the inner ring (5-position) rather than the outer ring. In states of severe illness or starvation, the body shunts T4 metabolism toward the inactive rT3 to conserve energy.
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