Low Thyroid Conversion of T4 to T3

Most common Thyroid markers are TSH (thyroid stimulating hormone), free T4, and free T3. But often doctors will only test TSH. ⠀
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Although the thyroid gland secretes only a little T3, it is the most active form the body can use. T4 must be converted to T3 before the body can use it. Most of this conversion happens in the liver, but also take place in cells of the heart, muscle, gut, and nerves. So you can see why it’s not always as simple as taking a supplement which contains nutrients to support the conversion of T4 to T3. ⠀
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Only about 60% of T4 is converted into usable T3. 20% becomes reverse T3 (rT3), an inactive form the body cannot use. Levels of rT3 can become too high in times of stress, major trauma, surgery, chronic illness and sometimes when doing prolonged intermittent fasting. ⠀
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About 60% of the conversation of T4 to T3 happens in the liver. The liver metabolises hormones, filters toxins, and cleans the blood. Byproducts from these processes are dumped into the gallbladder for final removal. Low thyroid function bogs down this whole process, making the liver and gallbladder sluggish and congested. As thyroid hormones are converted into a usable form in the liver, liver function greatly affects conversion of T4 to T3. ⠀
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When the liver cannot properly break down hormones for elimination, they can go back into the bloodstream in an even more toxic form than when they entered the liver. This is especially true with oestrogen. Elevated oestrogen directly affects thyroid function by reducing the liver’s conversion of T4 to active T3, so that thyroid hormones can’t get into the body’s cells. You can check your risk factors for hormone detoxification with DNA testing. ⠀
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The intestines convert about 20 % of T4 into T3, but only in the presence of enough healthy gut bacteria. These bacteria serve many functions, one of which is to facilitate the conversion of T4 to T3. When diets and digestion are poor, an overabundance of bad bacteria occurs, crowding out the beneficial bacteria and hindering thyroid conversion.