blood thyroxine level blood triiodothyronine level calculated blood thyroid hormone level blood triiodothyronine to thyroxine ratio 2013-01-11T11:28:42Z A calculated measurement in which the amount of triiodothyronine in a specified volume of blood is divided by the amount of thyroxine in the same sample and presented as a ratio, fraction, quotient or percentage, thus normalizing it to thyroxine level. CMO:0001361 EFO:0009779 JSmith blood T3 to T4 ratio clinical_measurement_ontology tri-iodothyronine/thyroxine ratio measurement