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Thyroid Test List And Deiodinases

By Lucy Rose Clinic

May 24, 2021

Thyroid Testing and Examination

Here is the list of thyroid specific testing:

  • Thyroid stimulating hormone (TSH): This test is the initial indicator or thyroid disorders. TSH is produced by the anterior pituitary gland after stimulation from thyrotropin releasing hormone (TRH) secreted by the hypothalamus. TRH then triggers the pituitary gland to release TSH. The level of TSH rises when thyroid hormone levels (T4) in the blood decline. Conversely, the level of TSH declines as the thyroid hormone (T4) level in the blood rises.
  • Free T4 – Measures thyroxine that is not attached to proteins. This level of free hormone is what exerts the biological effect. This test shows how the hormone affects the functioning of many types of body cells.
  • Triiodothyronine (Free T3): Measures the level of T3 in the blood. This is the active form of thyroid hormone and exerts direct influence to the cells. If your Free T3 levels are low or high you will have symptoms.
  • Antithyroglobulin (anti-Tg) antibodies: This test is used to diagnose autoimmune thyroid disease. (Graves’/Hashimoto’s Diseases). 
  • Antithyroid peroxidise (anti-TPO) antibodies: This test is used to diagnose autoimmune thyroid disease, in particular Hashimoto’s Disease.
  • Reverse T3: This is created by the body from T4. Your body can either turn T4 into T3 or into reverse T3 based on what it needs. Factors that convert too much reverse T3 include high cortisol (stress), and poor liver function (fatty liver or methylation factors). 

Below is an example of a functional thyroid test showing these markers.

Why We Need Further Functional Testing

Once the thyroid hormone is happily swimming around your body via the bloodstream, it is not a sure thing that it will enter the cell and exert it’s action on the mitochondria. It needs to get past the cell wall. It has been thought that thyroid hormone enters the cell through passive diffusion, but researchers are now thinking it is more complicated than that.

Some researchers propose a membrane-mediated process of entry. The involvement of saturability, high specificity, sensitivity to temperature, sulfhydryl and cell-surface-perturbing reagents and hydrolytic enzymes.

This research highlights something we have known for years at The Lucy Rose Clinic. Just because there is ample thyroid hormone in the blood, does NOT mean you are getting all the metabolic advantages of it.

Down the rabbit hole

Conversion of thyroid hormones is controlled by enzymes, and these enzymes need specific nutrients to do their job.

Deiodinase type 1, type 2, and type 3 are the set of three enzymes that convert thyroid hormones in the human body. They are abbreviated D1, D2, and D3.

  • D1 focuses on converting RT3 and T3-Sulfate, and we still know little about T3S.
  • “D2 and D3 are usually not expressed together in the same cell” (Groeneweg, 2017)
  • D2 focuses on converting T4 into T3. It does not convert it into rT3.
  • A high rT3 issue is mediated by cells expressing too much D3.

In a person with a healthy thyroid, D2 and D3 are balanced throughout the body, and are ready to respond and adjust to changes in thyroidal secretion rate, thyroid secretion ratio, and health and environmental conditions.

When the body or a local tissue is attempting to compensate for illness, damage, and/or excess or low thyroid hormone, the deiodinases will become imbalanced by D3 dominance. It is essentially a self protective mechanism – but under certain circumstances can go awry.

This is one reason people can have so much trouble balancing thyroid medication.

Can we treat this?

The field of study that focuses on improving the health and status of your enzyme production is called Epigenetics.

“Epigenetics is the study of heritable changes in gene expression (active versus inactive genes) that do not involve changes to the underlying DNA sequence — a change in phenotype without a change in genotype — which in turn affects how cells read the genes.”

Scientists have discovered genetic polymorphisms in the genes DIO1 and DIO2 that make T4-T3 conversion less efficient.

However, having a genetic polymorphism is only a small fraction of the problem. My favourite quote that explains this is;

“Genes load the gun. Environment pulls the trigger”.

A large part of the function of these enzymes is regulated epigenetically, by environmental stimuli such as age, lifestyle choices, diet, toxin load, and disease status. And that is something we do have a lot of control over.

This is where we SHIINE!

Now it’s your turn! Book a free 15-minute consult to start your Ultimate Thyroid Health Journey today!

The Lucy Rose Clinic prides itself on being at the forefront of thyroid treatment using functional pathology and scientifically validated natural medicine solutions, coupled with correct diet, exercise, detox strategies, and lifestyle guidance to address all factors required to get you feeling well again.


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