04/10/2026
THIS!!!!
Levothyroxine normalizes blood tests but leaves tissues starved of thyroid hormone. That's why so many people on levo have clear hypothyroid symptoms, even with normal labs.
Researchers gave rats levothyroxine and found it left their tissues starved of thyroid hormone T3 - even though their blood tests were normal.
Levothyroxine only causes hidden hypothyroidism.
In the experiment, researchers removed the rats' thyroid glands, so the rats produced no thyroid hormones.
The researchers then administered T4 (levothyroxine) directly into the rats' blood for a week.
This resulted in normal TSH and T4 levels in the rat's blood. Their labs were fine!
Most doctors believe this means there is no problem with thyroid hormone levels.
BUT it is low levels of T3 in cells that cause hypothyroid symptoms. Rats and people have to convert levothyroxine (T4) into the active thyroid hormone T3.
When the researchers looked, they found that most tissues were deficient in T3 - even though the basic labs looked fine.
Tissue levels of thyroid hormone (T3) were only replenished when the animals were also given T3.
Lots of people are suffering from hypothyroid symptoms (low tissue T3), which are hidden from basic testing, due to the insistence that levothyroxine-only (T4) is a sufficient treatment and that TSH/T4 are sufficient tests to exclude hypothyroidism.
Levo/T4 treatment does not guarantee that tissues receive an adequate amount of thyroid hormone (T3).
"T3 in plasma and most tissues and plasma TSH only reached normal levels when T3 was added to the T4 infusion. The combination of 0.9 microgram T4 and 0.15 microgram T3/100 g /BW.day resulted in normal T4 and T3 concentrations in plasma and all tissues as well as normal circulating TSH and normal or near-normal 5'-deiodinase activities. Combined replacement therapy with T4 and T3 (in proportions similar to those secreted by the normal rat thyroid) completely restored euthyroidism in thyroidectomized rats at much lower doses of T4 than those needed to normalize T3 in most tissues when T4 alone was used. If pertinent to man, these results might well justify a change in the current therapy for hypothyroidism." - Only the combined treatment with thyroxine and triiodothyronine ensures euthyroidism in all tissues of the thyroidectomized rat
[The man in the image was treated with NDT USP, which contains T3]