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Why test T3 and T4?
My husband has been having drenching night sweats for the past 8 months he has been taking 125 of levothyroxine daily for the past 2 years. His GP will only check his TSH levels and says they are fine. Can anyone please explain why T3 and T4 are required so he has a good argument to go back to GP with?
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T3 and T4 are the actual hormones produced by the thyroid. The thyroid produces and secretes the T4 Hormone, since it binds with protein, some is lost, the remaining T4 is called Free T4, then the Free T4 is converted mostly by the Liver, it is converted to T3, after, some again is lost due to binding with or attaching to protein, the remaining is known as Free T3, This free T3 is what the body/cells needs to function. When the free T3 is low, the Pituitary Gland located in the brain, acts like a sensor, it then send another hormone TSH (Thyroid Stimulating Hormone) to the thyroid to "Bump" it or stimulate it into producing more T4, So the lower the hormone output of the thyroid, the higher the TSH. MD's who are good with thyroid treatment  use TSH to indicate if a thyroid disease is present, once the thyroid disease is diagnosed Free T3 and Free T4 along with the patients symptoms should be used to guide treatment and dosage not TSH. If you can get the MD to do these tests, request a copy of the results, post them here and we will explain them to you and comment/advise on treatment and dosage. please include the levels and reference ranges provided for each. We are not MD's although we have all been through your husbands experience with MD's  Good Luck FTB4
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Thank you for your prompt and informative answer. Very much appreciated!
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I'd just add that once on meds, TSH often becomes unreliable.  Many people start taking meds and TSH drops to almost zero and stays there.  It can no longer be used to determine thyroid status.

If your doctor won't test FT3 and FT4, you might want to look for a doctor more informed on thyroid treatment.  In the meantime, if you want a quicker solution, you can order tests online.  A doctor's order isn't necessary, and the results are sent directly to you.  YOU will then know if FT3 and FT4 levels are adequate (we can help you interpret them if you post them here).  Healthcheckusa is one site that members have had good luck with, but there are other choices as well.  Your current doctor might be more responsive if you see him with "abnormal" results in hand.
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