fT3/rT3 ratio

Free T3 to reverse T3 ratio reflects the balance between thyroid hormone activation (T4→T3) and inactivation (T4→rT3).
Also known as:
fT3-rT3-ratio
.
Enter values
 
Value
Unit
fT3
rT3

fT3/rT3 ratio ranges

According to OptimalDX, fT3/rT3 ratio should be between 10 and 28:
10
28
Risk Scale
Optimal range for fT3/rT3 ratio appears to be between 10 and 28:
0
10
28
50

Free T3 to reverse T3 ratio reflects the balance between thyroid hormone activation (T4→T3) and inactivation (T4→rT3).

There are multiple competing formulas, this uses the most common one: (fT3 in pg/mL ÷ rT3 in ng/dL) × 100. Some formulas also use total T3 instead of free T3.

fT3/rT3 ratio interpretation

For low

Shift toward increased thyroid hormone inactivation (higher rT3, lower T3) is driven by systemic illness, inflammation, energy deficit, or organ dysfunction rather than an "thyroid problem".

For high

Shift toward decreased thyroid hormone inactivation (lower rT3, higher T3).

  • With low PTFQI it is supportive of central hypothyroidism.

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Zsolt Szabo
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