Could low Free T3 be causing you ongoing issues?
There are binding proteins that attach to thyroid hormones to travel through the blood vessels, to cells all over our body. When they reach the cells, only the unbound “free” hormones can actually be used by the cells. Therefore Free T3 levels (and Free T4!) are important to monitor. It’s important to be aware that F ree T3 and Free T4 are different to Total T3 and Total T4, with Total being pretty much useless. Make sure you check Free.
It’s more common than you think, inadequate Free T3 issues. Often, doctors tend to just test our TSH alone and when it comes back ‘normal’, they declare us ‘normal’ and send us on our way. Sound familiar?
However, TSH alone isn’t accurate, and if we have on going issues such as mental health problems, abnormal blood pressure and heart disease (stroke, heart attack, heart failure, cardiac arrest, artery disease), then its possible that a low Free T3 could be the culprit. The cardiovascular system is one of the most important targets on which thyroid hormones act. A low Free T3 leaves you hypothyroid, even if you have a ‘normal’ TSH and even a ‘normal’ Free T4, too. It leaves us with symptoms and other issues, as we stay inadequately treated.
The issues that low Free T3 cause, can even occur with subclinical/borderline hypothyroidism, where TSH levels are declared ‘not that bad’.
The bottom line is: you must make sure you’re having a FULL thyroid panel checked. Always.
The only way to make sure your Free T3 isn’t causing you any issues or putting you at risk of developing issues or other conditions, is to complete a full thyroid panel, and ensure that your levels are optimal.
So how does a low Free T3 occur?
Both thyroid hormones T4 and T3 are related to heart disease because they affect the heart rate and the amount of blood pumped by the heart. Thyroid hormones help your blood flow smoothly by relaxing the muscles of your blood vessels and keeping your blood vessels open. Hypothyroidism can also lead to high cholesterol, as well as stroke, heart attack, heart failure, cardiac arrest, artery disease etc.
This study concluded that low Free T3 is a strong predictor of death in cardiac patients and might be directly implicated in the poor prognosis of cardiac patients. Clinical and experimental evidence has shown that T3 plays a major role in modulating heart rate and cardiac contractility as well as arterial peripheral resistance.
In addition to heart problems, low Free T3 can also cause mental health issues such as depression and anxiety.
T3 has an important role in the health and optimal functioning of your brain, including: your cognitive function, ability to concentrate, mood, memory and attention span and emotions and ability to cope with life’s stresses. Christiane Northrup, MD explains this further on her website, “[T3] is actually a bona fide neurotransmitter that regulates the action of serotonin, norepinephrine, and GABA (gamma aminobutyric acid), an inhibitory neurotransmitter that is important for quelling anxiety.” She also states: “If you don’t have enough T3, or if its action is blocked, an entire cascade of neurotransmitter abnormalities may ensue and can lead to mood and energy changes, including depression.”
T3 interacts with brain receptors and makes the brain more sensitive to chemicals such as Serotonin and Norepinephrine, which affects your alertness, memory, mood and emotion.
Issues caused by a low Free T3 can boil down to simple under treatment of your thyroid disease, i.e. you not being on enough thyroid hormone replacement medication. It can also be caused by an enzyme called iodothyronine deiodinase that is either deficient or not compatible for some people. The enzyme iodothyronine deiodinase is important in the activation and deactivation of thyroid hormones. T4 is converted into T3 by deiodinase activity. A problem with this can therefore cause conversion issues, where TSH can look ‘fine’, as well as Free T4, but with a low Free T3 and continued hypothyroid symptoms and development of other health conditions (such as mental health and heart/blood pressure problems).
If you are on T4-only medication such as Levothyroxine, Synthroid etc. and still don’t feel fully well, then it is likely you could not be converting T4 to T3 and are experiencing the above issues.
Low T3 syndrome is when you have low blood serum concentrations of Free T3, which can be accompanied by a high Free T4, which demonstrates a conversion issue, often also with high concentrations of reverse T3.
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