The “Choosing Wisely Canada” toolkit promoting limitation of Free T3 and Free T4 testing has been the food for some meme refutations.
Choosing Wisely Canada. (n.d.). Toolkit: Less is More with T3 & T4. Retrieved December 30, 2018, from https://choosingwiselycanada.org/perspective/toolkit-t4-t3/
Recently, we’ve focused on their Table 2 which outlines situations they recommend NOT to order Free T4 or Free T3.
There are no research citations on these claims. They are based on opinion and false, weak reasoning.
Notice that their Table 2 indiscriminately combines and mixes “screening” situations and “therapy” situations.
This confusion between screening and therapy is a problem. It is a false analogy between unmanipulated vs. medically manipulated thyroid hormone levels. Science has proven that TSH behaves differently in thyroid therapy than it does in a human body that is unmanipulated by oral dosing of thyroid hormones.
The distinction between the two situations is important. Screening untreated patients by the TSH works to some extent, but therapy by TSH alone cannot ensure optimal thyroid hormone levels within the reference range.
Next we focused on just the Table 2 dictum against measuring Free T3 in any T3-based therapy.
It seems doctors are so averse to hormone fluctuations even when they are beneficial to patients.
They falsely believe there is no way to handle them in lab testing.
Most of us on T3-based therapy are not children. We can understand how to time our tests so that results are not influenced by the swift rise and fall of Free T3 that occurs over the first 8 hours after a dose.
The next meme focuses on the flimsy argument against Free T4 testing in desiccated thyroid therapy:
First of all, you can’t forbid any test based on an biased “bet” on the most common or expected result.
The reason to test Free T4 is to give you information that is useful in optimizing therapy, not merely to get a result flagged as “normal” or “low” or “high.”
Secondly, the assumption “often low” is false.
In desiccated thyroid therapy, higher doses can certainly result in Free T4 levels that are in the upper part of reference range. Desiccated thyroid contains 80% T4 and 20% T3.
The only truism regarding desiccated thyroid therapy is that it is often the case that Free T4 is lowER in its reference range than Free T3.
A LOWER FT4 is necessary and beneficial because lowering T4 enables the patient to achieve optimal Free T3 without causing hyperthyroidism from excess T4-T3 conversion.
Finally, as the meme says, if you expect the result to be low — that’s MORE reason to test it in order to ensure that you raise the dose to adjust the FT4 level in light of the Free T3 level.
This “often low” reasoning is even more annoying given the fact that the American Thyroid Association forbids Free T3 testing in hypothyroidism because T3 is often “normal” in untreated early autoimmune hypothyroidism.
Notice the contradiction. Is “often low” better than “often normal” as a justification to avoid testing?
CONCLUSIONS
Doctors, you must resist this false reasoning.
Please think clearly about good reasons why you would want to test Free T4 or Free T3 — namely, to prevent isolated deficiencies in either hormone that can and do often hide under a normalized or low TSH in this form of therapy.
Not testing Free T3 and Free T4 can lead to grave, long-term human suffering.
A narrow MONO-testing policy incorrectly assumes that pituitary TSH speaks for T3 sufficiency in blood and all peripheral tissues.
Serum levels of Free T4 and Free T3 do matter for health, as we have demonstrated with scientific research cited in our Campaign Statement and many posts.