Millions of people in America suffer from hypothyroidism and don’t even know it, because their doctor has missed the diagnosis as a result of not ordering the correct lab work. The majority of physicians opt to follow a subminimal protocol when ordering labs, and in the case of the thyroid, this only includes looking at thyroid stimulating hormone (TSH), which is a hormone produced in the pituitary.
Unfortunately, this is not enough to make a diagnosis of hypothyroid, because a patient’s TSH can be in the normal range in hypothyroid cases that involve under conversion of T4 (thyroxine) into the bioactive thyroid hormone T3 (triiodothyronine); the majority of which is metabolized in periphery.
What exactly is conversion?
The thyroid gland itself produces very little T4 and T3, in fact, 90% of what the thyroid releases is in the form of T4, which is converted into T3 (10xs more potent than T4) in peripheral tissues like the liver, kidneys, heart, brain, etc. This means that about 80% of the active thyroid hormone (T3) is produced outside the thyroid gland itself, with most of this taking place in the liver. When certain enzymes (iodine, tyrosine, glutathione, selenium, zinc, etc.) act on T4 it’s converted into bioactive T3, which is then pushed onto the receptor by vitamin D; of which many Americans are deficient.
What does thyroid hormone do?
What are some of the main causes of under conversion?
In my experience, under conversion in the American population is caused by a combination of factors that stem from the American lifestyle and the Standard American Diet (SAD diet). Contributing factors include:
Why Free T4 and Free T3 have to be tested?
Total T4 and Total T3 are not accurate indicators of how much of the hormone is availablefor the body to use, because they are bound to protein in the blood.
In contrast, Free T4 and Free T3 are not bound to any proteins, and therefore can be utilized by the body.
What should be tested and what are the optimal health ranges?
The only way to make an accurate assessment is to order a complete thyroid panel, which includes not only TSH, but also Free T4 and Free T3; all of which must be tested together, NOT SEPARATELY, since they are all relative to one another and can fluctuate due to certain variables.
For patients who have a history of autoimmune symptoms it is strongly recommended to also test for antibodies:
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