PTFQI

Quantifies pituitary TSH sensitivity to free T4 using standardized z-scores, improving stability at extreme hormone values.
Enter values
 
Value
Unit
TSH
fT4

PTFQI ranges

According to Kratzsch et al. (2005), PTFQI should be between -0.7 and 0.7:
-0.7
0.7
Risk Scale
Optimal range for PTFQI appears to be between -0.4 and 0.4:
-1
-0.7
-0.4
0.4
0.7
1
Why this optimal range?
Ranges are based on standard deviations from the mean. Values in red (±2 SD) indicate significant deviation from expected pituitary-thyroid feedback; values in yellow (±1-2 SD) indicate moderate deviation.

Quantifies pituitary TSH sensitivity to free T4 using standardized z-scores, improving stability at extreme hormone values.

There is only one study Kratzsch et al. (2005) that used strict criteria for healthy thyroid function (NACB criteria + normal ultrasound) so the parameters to calculate PTFQI are used from this study.

PTFQI interpretation

For low

Low PTFQI means that TSH is lower than expected for the given FT4, reflecting apparent pituitary over-sensitivity or impaired TSH secretion. Very low values may support a diagnosis of central (secondary/tertiary) hypothyroidism.

For high

High PTFQI indicates TSH is higher than expected for the given FT4, most commonly seen in subclinical hypothyroidism or reduced apparent pituitary sensitivity.

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Zsolt Szabo
Zsolt Szabo
Precision Health Consultant for Longevity Clinics, Biohacker, and Software Engineer

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