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Thyroid Function Interpreter

Comprehensive assessment of thyroid function blood tests (TSH, fT4, fT3, rT3, ...) designed to detect thyroid-related dysfunction early.

For now, it only works for patients who are not on any thyroid medication and are not pregnant or postpartum.

Enter values
all fields are optional
 
Value
Unit
TSH
fT4
fT3
 
Extended
rT3
TPOAb
TRAb
This tool is for informational purposes only and not intended for diagnosis.

Simplified HPT Axis Overview

Pituitary & HypothalamusApparent sensitivityPTFQITSHThyroidSPINA-GTanti-TPOTRAbfT4Hormone reservoirfT3Active hormonePeripheral T4→T3SPINA-GDD1 & D2fT3/fT4 ratio:—D3rT3Inactive hormoneNegative Feedback (T3)Negative Feedback (T4)
Optimal
Suboptimal
Abnormal
Unknown
Pituitary sensitivity

PTFQI: 000

Estimated pituitary TSH sensitivity to free T4, maintaining stability at extreme hormone values.
-1
-0.7
-0.4
0.4
0.7
1

TSHI: 000

Quantifies pituitary TSH sensitivity to free T4. Commonly used, but less reliable at extreme hormone values.
0
1.35
1.69
3.71
4.05
5

PTFQI-FT3: 000

Estimated pituitary TSH sensitivity to free T3. This is a newer, less validated index, but may add value in some contexts.
-1
-0.7
-0.4
0.4
0.7
1
Thyroid secretory capacity

SPINA-GT: 000 pmol/s

Estimated maximum thyroid hormone production capacity of the gland under TSH stimulation. Not sensitive to isolated secondary (pituitary) disorders.
0
1.41
2.32
7.76
8.67
15
Peripheral conversion / deiodinase activity

SPINA-GD: 000 nmol/s

Estimated maximum peripheral T4 to T3 conversion. Unlike simple FT3/FT4 ratios, it accounts for nonlinear enzyme kinetics.
0
20
25
35
40
60

FT3/FT4 molar ratio: 000 mol/mol

A crude proxy for peripheral T4-to-T3 conversion (deiodinase activity).
0.1
0.27
0.29
0.38
0.42
0.6

fT3/rT3 ratio: 000 (pg/dL)/(ng/dL)

Free T3 to reverse T3 ratio reflects the balance between thyroid hormone activation (T4→T3) and inactivation (T4→rT3).
0
10
28
50
Thyroid Antibodies
TRAb:
N/A
TPOAb:
N/A

Estimated prevalence of antithyroid antibodies (in percent)

GroupTRAbTgAbTPOAb
General population0%5 to 20%8 to 27%
Graves' disease80 to 95%50 to 70%50 to 80%
Autoimmune thyroiditis10 to 20%80 to 90%90 to 100%
Relatives of patients with autoimmune thyroiditis0%30 to 50%30 to 50%
Type 1 diabetes0%30 to 40%30 to 40%
Pregnant women0%~14%~14%

Source: UpToDate

Individual Thyroid Markers

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
20

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
3.5

fT3: 000 pg/mL

Free T3 is the active thyroid hormone driving metabolism (the "gas pedal").
0
2
2.8
4
4.4
8

rT3: 000 ng/dL

Reverse total T3 is an inactive metabolite of T4. It is useful for differentiating euthyroid sick syndrome from central hypothyroidism.
0
8
10
20
24
60

Why this beats ChatGPT

Thyroid Function Interpreter visualizes all hormones, calculated sensitivities, and secretory capacities on the HPT axis diagram, with each node colored by status so the type of dysfunction is immediately apparent. Chatbots don't do that.

All research is done by humans. AI helps with coding and refining text for better readability.

About the site author

My personal mission is to extend human lifespan by collectively adding 1 million years to people's lives.

That’s why I made this site 100% free, no sign-up, no email. Just instant results.

Zsolt Szabo
Zsolt Szabo
Precision Health Consultant for Longevity Clinics

How would you improve this tool ?

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