Biomarker Reference · fT3:fT4
Free T3 to Free T4 Ratio (fT3:fT4) is a clinical biomarker used in thyroid-endocrine assessment. The free T3 to free T4 ratio reflects the efficiency of peripheral conversion of T4 to T3 by deiodinase enzymes. It is measured in 1 laboratory test on BiomarkersLabs.com.
The free T3 to free T4 ratio reflects the efficiency of peripheral conversion of T4 to T3 by deiodinase enzymes. A low ratio may indicate impaired conversion due to illness, nutritional deficiency (selenium, zinc, iron), inflammation, or medication (beta-blockers, corticosteroids), while a high ratio can occur in hyperthyroidism or preferential T3 secretion.
The fT3:fT4 ratio is used in functional and integrative practice to identify conversion insufficiency when fT4 is normal but fT3 is disproportionately low. It guides decisions about combination T4/T3 therapy, though mainstream endocrinology does not universally endorse this metric.
Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.
1 test on BiomarkersLabs.com include this biomarker.
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