Free T3 is the most important thyroid hormone in the body. However, it is also a hormone that most conventional doctors don’t check.
Now is when you tell me, “I’ve had my TSH checked many times and my doctor says it’s just fine.” Yes, TSH is the standard measuring stick, if you will, for how well your thyroid is functioning. Normal levels of TSH are between 0.4 and 4.0-4.5 mIU/L. But, many times TSH is misleading if one does not consider that Free T3 can be low even with a completely normal TSH levels. TSH is produced only when the body senses that not enough thyroid hormone is being produced. If your body is making plenty of T4 and even T3, but that is not translating to enough unbound Free T3, TSH levels are meaningless. Free T3 levels should be between 2.0-4.4 pg/ml. This may vary depending on the lab used to evaluate blood levels.
Without adequate Free T3 levels, a person may feel fatigued, have mood problems like depression or anxiety, be inappropriately cold, have dry, brittle hair and dry skin, struggle with losing weight, and/or have high cholesterol. The opposite is true of too much T3. Heart palpitations, an inability to gain weight, anxiety, muscle weakness, and insomnia are all symptoms associated with hyperthyroidism. None of that sounds good, so it would be of benefit if you are having any of these symptoms to see your healthcare provider and ask that they check your thyroid levels including a Free T3 levels.
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This article also mentions an underactive thyroid as a cause of depression. The article also mentions that your thyroid can be checked with a TSH test. However, we know that if your body is not converting T4 to T3 you are still going to suffer with symptoms including depression. ( See story above).