Thyroid Function Tests measure...

the concentration of thyroid-related hormones (TSH, T4, T3, rT3) in serum or urine and/or the presence/amount of auto-antibodies present that may alter thyroid function.Tests are usually carried out on blood or urine. Blood tests are most commonly used to assess thyroid health.

Abbreviations

T4 is thyroxine, the INACTIVE form of thyroid hormone.T3 stands for tri-iodothyonine, the ACTIVE form of the hormone.The thyroid gland also produces T2 and T1 hormones.The numbers indicate how many iodine atoms are present in each hormone.

Total T4 or T3 (tT4, tT3) is the concentration of T4 or T3 hormone bound to carrier proteins present in your blood. tT4 & tT3 measurements will vary depending on how much carrier protein is present in your blood.

Free T4 or free T3 (fT4, fT3) is the concentration of unbound hormone in your blood. Most tests measure fT4 and/or fT3 as this better reflects thyroid function

Thyroid Stimulating Hormone (TSH) is the amount of TSH released by the pituitary gland.This stimulates the thyroid gland to increase T4 and T3 production

Reverse T3 is an inactive mirror image of the T3 hormone that can bind to and block T3 receptors from binding T3 and participating in energy production

Thyroid Auto-antibodies alter how well your thyroid functions. They are produced by your immune system in error and interfere with normal thyroid function altering the amount(s) of thyroid hormone produced.

90% of thyroid disorders (Graves' Disease & Hashimoto's Thyroiditis) are autoimmune and involve at least one of the thyroid auto-antibodies below.

Thyroid Peroxidase Auto-antibody/Thyroid Microsomal Auto-antibody (TPO Ab) reduces T4 & T3 production leading to Hashimoto's thyroiditis/ hypothyroidism

Thyroglobulin Auto-antibody (TG Ab) can cause over- or under-production of thyroglobulin leading to Hashimoto's Thyroiditis/hypothyroidism or Graves' Disease/ hyperthyroidism

Thyroid Stimulating Immunglobulin (TSI Ab) affects TSH receptors stimulating over-production of T4 (Graves' Disease/hyperthyroidism)

Test Reference Ranges

Reference ranges vary depending on the test you use. You must check your results against the reference range for the test you do. Below are indicative ranges for some UK blood tests that represent the results range for a healthy population.

TSH
free T4
free T3
reverse T3
TG Ab
TSI Ab
TPO Ab

British Thyroid Foundation*

0.4 - 4.5
9 - 25
3.5 - 7.8

Myrios/Medichecks

0.24 - 4.20
12 - 22

units

mU/litre

pmol/litre

pmol/litre
IU/millilitre
IU/millilitre
IU/millilitre

Genova/IWDL

0.24 - 4.20
10 - 22

2.8 - 6.5

0.14 - 0.54

0 - 40

0 - 35

Thyroid Tests & Terms Explained

Results and What They Mean

Some patients remain symptomatic despite their results being 'in range'.

For more on this

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Summary of Common Thyroid Function Tests Results & their Significance*****

* British Thryoid Foundation - www.btf-thyroid.org

** Medichecks - Antibody Panel 1 Test Results Report

*** Myrios HypothyroidismTest Results Report

**** Genova Diagnostics Thyroid Plus Test Results Report

***** "Thyroid Disease - The Facts" by Mark P.J. Vanderpump and W. Michael G. Tunbridge

Thyroid function tests measure the concentration of thyroid hormones and auto-antibodies and are used to indicate thyroid health.
The problem is - test results can fail to reflect how you actually feel.

At WH360 we believe your symptoms and how you feel day-to-day is as - if not more - important than your test results.

Tests measure what they set out to e.g. serum concentrations of hormones in your body but you can still feel ill even if with test results that are

'in range'. If you have symptoms it's crucial to find out why no matter what the numbers say. There are many reasons why you could feel ill with test results that are 'in range' as there are other conditions with symptoms that overlap with thyroid disease.
For more on this

click here