Functional Endocrinology Standard
Cellular Resistance Metric
Deiodinase Evaluator
Cellular Resistance Metric
Deiodinase Evaluator
Reverse T3 to Free T3 Ratio Calculator (Cellular Resistance)
Evaluate whether elevated Reverse T3 is acting as a competitive inhibitor on nuclear thyroid receptors, blunting cellular energy and metabolism despite normal serum TSH blood tests.
Enter your Free Triiodothyronine (FT3) laboratory result.
Enter your Reverse T3 lab value (often ordered as total rT3).
Cellular Free T3 / Reverse T3 Assessment
Molar Conversion & Receptor Occupancy Index
Optimal Ratio
19.4
Calculated Ratio: [Free T3 (pg/mL) × 100] ÷ Reverse T3 (ng/dL)
Cellular Interpretation
Your ratio is within the optimal functional window (≥ 20). Nuclear thyroid hormone receptors receive sufficient active Free T3 without excessive competitive blockade from Reverse T3.
Clinical Reference Thresholds:
- Ratio ≥ 20: Optimal cellular thyroid signaling; minimal deiodinase 3 shunting.
- Ratio 15 – 19.9: Mild/Borderline resistance; common in chronic caloric restriction, mild anemia, or elevated cortisol.
- Ratio < 15: Significant Cellular Thyroid Resistance; Reverse T3 is actively occupying receptors, blunting mitochondrial energy production.