Understanding Thyroid hormones and Blood Tests

The function of the Thyroid is to regulate metabolic rate (energy production) and to stimulate growth in children.

The most common symptoms of Thyroid dysfunction (including sub-clinical hypothyroidism) include low energy and weight gain and general malaise. These symptoms are so common these days that they are considered normal – it’s truly the 20th century syndrome. Note that not all patients with functional hypothyroid are over weight). Hyperthyroidism, on the other hand, creates a speeding up of the metabolism and these people always be at least a little underweight.


There are stages of thyroid dysfunction.

Optimal – Beginning of signs/symptoms – Pathology (+ve tests) – Death

Doctors have pharmaceutical therapeutic intervention at the pathology stage. Practitioners like Dr Alice give intervention earlier in the process, when signs and symptoms first appear. She is looking for a sub-clinical problem.


What does a ‘normal’ blood test result mean?

When we get Thyroid blood tests we also have to remember that they are testing for pathology (disease) of the thyroid. If the doctor says that your test results are ‘normal’, he means you don’t have ­Thyroid disease. He is not testing for dysfunction of the metabolic pathways of the Thyroid; what we call ‘sub-clinical’ or ‘functional’, which precedes thyroid disease by 5-10 years.

We also need to bear in mind that the normal range for each of these tests is different for each lab. They take all the results they had that year for a particular test and find the average with a few standard deviations to each side.

Most people who are tested for thyroid hormones are either sick or on thyroid medication, which skews the data. Also, a pregnant woman’s test results would be different from an 80-year-old woman’s tests. The original Haines study that normal ranges are based upon, didn’t exclude people with diagnosed thyroid disease, nor with a sub-clinical thyroid problem. On your test results you can see that the normal range is the same for all people regardless of age, sex, and medication.

If you have had years of thyroid symptoms but have normal test results, be glad, not disappointed- more likely is that you have a sub-clinical thyroid problem. The doctor may ask you come back in 6 months and retest you, in case you have progressed from a functional problem to true, medicatable Thyroid disease.

In the meantime there are many ways that we can improve your thyroid function so you never progress to true Thyroid disease. However there are many causes of thyroid dysfunction (below), Dr Alice can discover which ones are affecting you.

It’s my goal to address the underlying cause of the problem.

-High cortisol from stress

-High levels of Estrogen (The pill, HRT, pregnancy, estrogen-mimicking toxins like plastics)

-Adrenal dysfunction

-Oxidative stress

-Long-term sugar abuse causing dysglycemia

-Whiplash – neck and cranial problems

-Iodine deficiency

-Chlorine, Fluoride and Bromide exposure

-Serotonin and Dopamine (neurotransmitter) deficiencies

-Heavy metal toxicity


-Radiation exposure – radioactive iodine and X-ray exposure

-Chronic infection

-Chronic Inflammation

-Vitamin D deficiency

-Leaky gut and Gluten sensitivity

-Deficiency of Vitamins -B3, B6, B12, Vitamin A and E (all required in the metabolic pathway of Thyroxin production)

-Deficiency of minerals – Zinc, copper, magnesium, selenium (also all needed in the metabolic pathway of Thyroxin production)

-Protein deficiency

If you are choosing to work with these factors remember that it took a long time for you to get sick and it will take time to get well again. Alice can provide you with long-term care, support, treatment and information.

What do my blood test mean?


Stands for ‘Thyroid Stimulating Hormone’, which is produced by the pituitary gland to stimulate the thyroid to produce T4 (Thyroxin). TSH is like a control tower that regulates Thyroid hormone levels, when they are too low the pituitary secretes more TSH, when they are too high (usually because of too much Thyroxin medication), the pituitary secretes less TSH.

So high TSH = Thyroid under-function.

Low TSH = Thyroid over-function.

Normal TSH is considered to be between 0.5 and 4.5, however integrative medical doctors and functional medicine practitioners consider anything over 2.2 to be high.

Sometimes doctors only test for TSH levels, and if they are outside the range of normal, only then will they go ahead and test for Total T4, T3, Free T3 and Free T4 rT3 (Reverse T3) and thyroid anti-bodies for Auto-immune disease. (all explained below)

What we do know is that TSH varies during the day, so it can change up to 50%. So if your TSH levels are actually 2, depending on the time of day you may shoe TSH between 1 and 3. Ideally we have more than one test and find the mean.


T4 and T3

T4 is converted to T3 in the liver and requires selenium and zinc, yet both hormones have a similar effect of increasing metabolic rate, but on different scales. T4 is only 10 percent as active as T3, so T3 is much more potent.



T4 Is called Thyroxin but its real name is ‘TETRA-iodo-thyronine’, some T4 is converted to T3.

People who have pathologically low levels of T4 take ‘Thyroxin Sodium’ which is the pharmaceutical solution. Normal levels of T4 are between 9-26. If your levels are even slightly below 9 you will be prescribed Thyroxin Sodium.

40% of T4 becomes normal T3 to drive metabolism and 60% becomes Reverse T3 (rT3) to slow it down again. (See below)



T3 is ‘TRI-iodo-thyronine. You can think of it like the accelerator on your car.

T3 is 10 x more active than T4.

Normal levels depend on the lab but are around 80-180ng/dl.


Free T4 and Free T3

Measuring total T4 and Total T3 tell us how much thyroid hormone the thyroid is making, but most thyroid hormone is strongly bound to proteins in the blood, only the Free T4 and Free T3 can bind to the receptor sites on the cells and exert their effect. Free T4 and Free T3 give us a better understanding of what’s really happening.

Free T4 (FT4I) is between 4-11

Free T3 (FT3) is between 230-619pg/d (notice the enormous range)


Reverse T3 (rT3)

Clears excess T4 from the body. If T3 is like the accelerator in a car, Reverse T3 is like the break.

High rT3 can be caused by iron deficiency, large changes in body temperature causing multiple enzyme dysfunction, excess estrogen (The pill, pregnancy or toxins and liver enzyme dysfunction), Fluoride, Chlorine and Bromide (a food preservative).

High rT3 that is still within the normal range can be managed without pharmaceuticals, but by the time is really high the best help comes from your GP, who can organise a compound chemist to make bio identical T3.


Thyroid Anti-bodies

The doctor will test you for these if the other tests are outside the normal ranges.

Hashimoto’s is an autoimmune disease where the patient has symptoms of hypothyroidism (sluggish, overweight) Here the body wrongly attacks its own thyroid gland cells. The doctor may test for thyroid antibodies called TPO and Thyroglobulin.

Grave’s disease is an autoimmune disease where the patient has symptoms of an over-active thyroid (heart palpitations, speedy, warmth, increase reflexes). It is tested by the presence of TSI (Thyroid Stimulating Immunoglobulin).