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FT3/FT4 Ratio Formula:
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The FT3/FT4 ratio is a calculation that compares the levels of Free T3 (triiodothyronine) and Free T4 (thyroxine) thyroid hormones in the blood. This ratio can provide insights into thyroid function and conversion efficiency from T4 to the more active T3 hormone.
The calculator uses a simple ratio formula:
Where:
Explanation: The ratio is calculated by dividing the FT3 value by the FT4 value, providing a dimensionless number that represents the relationship between these two thyroid hormones.
Details: The FT3/FT4 ratio can help clinicians assess thyroid function, identify conversion problems from T4 to T3, and guide treatment decisions for thyroid disorders. An abnormal ratio may indicate issues with thyroid hormone conversion or metabolism.
Tips: Enter FT3 value in pg/mL and FT4 value in ng/dL. Both values must be greater than zero for accurate calculation.
Q1: What is a normal FT3/FT4 ratio?
A: Normal ranges can vary, but typically a ratio between 0.25-0.45 is considered normal, though reference ranges may differ between laboratories.
Q2: What does a high FT3/FT4 ratio indicate?
A: A high ratio may suggest hyperthyroidism, increased conversion of T4 to T3, or certain thyroid disorders.
Q3: What does a low FT3/FT4 ratio indicate?
A: A low ratio may indicate hypothyroidism, impaired conversion of T4 to T3, or certain non-thyroidal illnesses.
Q4: When should this ratio be measured?
A: The ratio is typically assessed when thyroid dysfunction is suspected, especially when standard thyroid tests are inconclusive or when conversion issues are suspected.
Q5: Are there limitations to this ratio?
A: Yes, the ratio should be interpreted in the context of clinical symptoms, other thyroid function tests, and individual patient factors. It's not a standalone diagnostic tool.