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Free T3 Conversion Ratios

Meaning

Free T3 Conversion Ratios quantify the efficiency with which the body converts the relatively inactive thyroid hormone thyroxine (T4) into its biologically potent form, triiodothyronine (T3), outside the thyroid gland itself. This ratio, often calculated or inferred from circulating levels of T4, reverse T3 (rT3), and Free T3, provides insight into peripheral deiodinase enzyme activity. Clinical relevance arises because suboptimal conversion often underlies symptoms of hypothyroidism even when TSH and T4 levels appear adequate. We monitor these ratios to assess the functional output of the thyroid axis at the tissue level. Maintaining a favorable ratio is paramount for cellular energy metabolism.