If a patient with Hashimoto's thyroiditis begins taking high-dose biotin supplements, which consequence follows regarding their thyroid hormone level measurements?

💡 Explanation

High-dose biotin interferes with streptavidin-biotin assays used to measure thyroid hormones, creating falsely low T4 values because biotin competes with T4 for binding. Therefore, the measured free T4 will appear reduced, rather than elevated. TSH and T3 uptake are less affected in typical assays.

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