Basic Take Home: All Thyroid Hormones are not made Equal – Past 2

Thyroid Health

In part 2 of this series of thyroid blogs, we are going to look at thyroid function and thyroid hormone production.

To read part one of this series, about the importance of toxic load and thyroid function, click here

This blog addresses the biochemical function of the thyroid and how to ensure a good production of this life-giving thyroid hormone, which seems to be in short supply with many thyroid conditions.


Think about this in terms of more than thyroid gland or thyroid hormone supplementation.

  1. Our thyroid makes 4 different thyroid hormones (T1, T2, T3 and T4) and the basis or raw materials of these hormones are made or produced from iodine, selenium, vitamin B1, B2 and the amino acid tyrosine. The body needs adequate amounts of these substances to produce adequate hormones. To ensure you have sufficient iodine, an iodine loading test may be helpful.
  2. Iodine deficiency is so wide spread, because our soils are so deficient. Ensure that you are eating iodized salt, seaweed products, fish, egg and prunes. Remember that in the 1970’s – 1980’s they changed out the iodine in our grains for bromine as a flour improver which actually blocks the effect of iodine and causes a relative deficiency in our food supply. This combined with flame retardants which are used commercially in our cars and furniture all plays a part in iodine deficiency.
  3. If you drink chlorinated and fluoridated water, it also has a rate limiting effect on iodine absorption in the body. Ensure your water does not contain these substances by getting an appropriate filter.

Let’s explain to you how the thyroid hormonal system works to ensure that your metabolism and metabolic functions are operating well, i.e. you have energy, are able to move around, do not suffer depression or low mood, have regular bowel movements and do not have cold extremities.

The thyroid hormones, specifically T3 act on the receptor sites in the tissues to cause the desired effect. If there is too little T3 you can have hypothyroid symptoms.

I will now give a brief overview on how the thyroid cascade of hormones work with each other to run your body’s metabolism optimally.

  • T4 is the major hormone, called a storage hormone which is used almost as a carrier. It is not physically active, but is the base substance that is used to convert into T3 hormone.
  • When T4 is converted to T3 hormone which is the active thyroid hormone, it can then exert its effect on thyroid function. T3 is much more metabolically active and speeds up metabolism, removes fatigue, aches and pains and low mood.
  • T3 is about 4-10 x more active than T4.
  • T3 is transformed from T4 by an enzyme (deiodinase) that removes one of the iodine molecules from T4 to make it a T3.
  • T2 is a hormone that helps to produce the enzyme deiodinase which converts T4 to T3 and helps to burn fat.
  • T1 is a hormone involved in keeping thyroid function in check and regulating the heart.

Can you now see why regular conventional medical treatment and prescription of T4 hormone has many flaws and down falls? Can you now see why T4 supplementation is not the complete answer to thyroid gland supplementation, and why thyroid homeostasis is often impossible by just being prescribed Levothyroxin or euthyrox or similar T4 pharmaceuticals? This is why so many women are on thyroid medication for years and are still sick!! – THEY ARE BEING GIVEN THE WRONG THYROID HORMONE!!

This is because your body may be unable to convert sufficient T4 to metabolically active T3 due to metabolic blockages in liver function, but the more efficient your liver is at conversion of T4 to T3, the less hypothyroid symptoms you will have.

  • There are co-factors that assist those thyroid deiodinase enzymes to function optimally and if you have a deficiency you will be unable to convert the T4 to T3 hormone.
  • This conversion occurs mainly in the liver, which means if you are having liver problems you will not to be able to normalize your thyroid without liver support.

Before we look at factors that reduce the conversion of T4 to T3, let us look at the enzymes that perform the conversion function.

Deiodinases- the heavy lifters in thyroid metabolism.

There are 3 different types of deiodinases (D1, D2, D3) and they remove the iodine molecules from the Thyroid hormones to change their form and function. They balance thyroid metabolism and hormone levels, but there are many factors in our environment that block or impede their enzyme function resulting in Hypothyroidism and hyperthyroidism.

We will look at deiodinases first and then the aspects that change their ability to function which ultimately changes the rate at which T4 is converted to T3.

  • D1 which acts on areas other than the pituitary – this is important because the pituitary is what secretes TSH hormone which causes the thyroid to be stimulated and upregulate.
  • D1 converts T4 to T3, in the peripheral tissues to a reduced degree of only 30-50%. As you can see, it has a sluggish action and is impacted by multiple physiological and emotional stressors. When this occurs, it is possible that peripheral tissues would have a reduced T3 level while the pituitary (under control of D2), shows an optimum level of T3. Could this be the reason why TSH is the incorrect marker to use for thyroid function?
  • D2 also converts T4 to T3, but 1000x more efficiently than D1.
  • D2 is the major stimulator of T3 throughout the body.
  • D2’s main area of action is the pituitary where it converts 80-90% of the inactive T4 hormone to active T3 hormone, driving cellular activity.
  • D2 has the opposite response resulting in an increase of T4 to T3 conversion within the pituitary. Because D2 is so powerful when levels of T3 in the pituitry are high and active, it may mean that there is a T3 deficiency in the tissues.
  • D3- downregulates the thyroid by converting T4 to Reverse T3(RT3), which reduces T3 sensitivity and production.
    D3 is found throughout the entire body except the pituitary and so only affects thyroid levels everywhere else by increasing RT3 and reducing T3- hence in the peripheral tissues thyroid function is reduced, thereby regulating thyroid activity.

Do you now understand that deiodinases are the missing link to the regulation of thyroid hormone and its effectiveness? It is not just about levels of thyroid hormones but the interplay between them, stress, sleep, inflammation, emf exposure, environmental toxicity and drug interactions that affect how well your thyroid is serving you. If you are suffering with a thyroid condition and possibly Hashimoto’s thyroiditis, concentrate on changing lifestyle factors to improve thyroid response.

Click here to read more from Dr Anthony De Pontes

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