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thyroid

type of blood test needed for diagnostic of underactive thyroid
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Avatar universal
thanks flyingfool what about any vitamin test
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Avatar universal
Be sure to specify the "free" test.

If you just ask for T4 and T3, you will almost certainly get the test for "total" hormone, rather than the biologicvally active "free" form of the hormone.

The "total"  test is considered obsolete and of little value.

The "free" test measures the amount of hormone that does NOT become attached to a protein.  Thus it is "free".  This is important designation because once the hormone gets attached to a protein it becomes biologically useless.  

ONLY the "free" hormones are used by the body.

The T4 hormone is a storage hormone.  That is it remains in the blood as "back up".  T4 is NOT used directly by the body's cells.  It first must convert into T3 (mostly in the liver).  And the free T3 hormone is the ONLY one used by the body at the cellular level.

To use a car analogy:

Think if the TSH test - (Thyroid Stimulating Hormone) as the thorottle position on your car.  The position of your foot on the thorottle is the indicator that tells your engine to speed up or slow down.   TSH is a hormone that is produced by the Pituitary gland in your brain.  It is supposed to accurately sense when there is too much or too little thyroid hormone in your blood.  And by secreteing more TSH, will be like pushing the accelerator peddal in your car, to speed up and have the thyroid gland produce more thyroid hormone.  Conversely if it senses too high of thyroid, it will produce less TSH and slow the thyroid gland from producing thyroid hormone.  When everything is working perfectly, the TSH level is supposed to be at a level number like a your car on cruise control going down the highway at a constant speed.  Another analogy woudl be to think of the pituitray and the TSH as like the thermosta in  your house.  which measures the temperature and tells the furnace to turn up or down.  Unfortunatly TSH is NOT that reliable, and your pituitary doesn't always sense things correctly.  kind of like a malfunctioning cruise control on your car.  Therefore it is HIGHLY recommended to actually test for the amount of fuel you giving your engine with the following two tests!

Think of Free T4 (FT4) as measuring the amount of fuel in the automobiles fuel tank. And think of Free T3 (FT3) as measuring the amount of fuel that actually gets to your cars engine.

Having an empty tank (very low FT4) will result in the engine not running at all or running poorly.  Similarly, even if the fuel tank is full (sufficient FT4 level), if the fuel line fully or partially clogged, not enough fuel will reach the engine and it will also result in a poor running engine.  

Symptoms you have are most directly correlated to the FT3 level.  Just as a cars engine's ability to run well is a result of sufficient fuel reaching the engine.
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Avatar universal
basically do these

TSH
Free T4
Free T3
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