A member asked:

What would cause a low t3 (liothyronine) level but normal tsh and t4 levels? would that be considered hypothyroidism?

2 doctors weighed in across 2 answers

No: Low t3 (liothyronine) with nl TSH and T4 is not hypothyroidism. Many things can make t3 (liothyronine) levels decrease such as illness, stress, colds etc. It is nonspecific and could also be lab error so low t3 (liothyronine) in the face of nl TSH and free T4 levels does not mean very much.

Answered 1/15/2015

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Birth control pills: If your TSH is normal you are not hypothyroid. T4 is converted to t3 (liothyronine) in your cells. The blood test measures t3 (liothyronine) that is bound to a protein in your blood and the active form of t3 (liothyronine). If you have too much or too little of the protein it can change the value of t3 (liothyronine). Birth control pills as well as other meds can effect the value.

Answered 6/10/2014

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