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PTFQI

Parametric thyroid feedback quantile-based index for FT4
Estimated pituitary TSH sensitivity to free T4, maintaining stability at extreme hormone values.
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Value
Unit

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.

Estimated pituitary TSH sensitivity to free T4, maintaining stability at extreme hormone values.

The parameters used to calculate PTFQI-FT4 were estimated from the medians and 95% reference intervals reported by Kratzsch et al. (2005) for a reference cohort selected using NACB criteria and normal thyroid ultrasound.

PTFQI interpretation

What a low value may mean:

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.

What a high value may mean:

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

Individual Biomarkers

See how each biomarker is interpreted on its own.

TSH: 000 µIU/mL

Thyroid Stimulating Hormone is a pituitary signal indicating how much thyroid hormone is requested.
0.3
1
2.5
4.4
10

fT4: 000 ng/dL

Free T4 is the circulating thyroid hormone reservoir that must be converted to become active.
0.4
0.97
1.4
1.7
2.5

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