Also Known As: Thyroxine (T4) and triiodothyronine (T3)
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T4 is made by the thyroid gland and converted to T3 by the liver. These hormones control energy production (metabolic rate) in tissues.
As follow up to an abnormal TSH test. Laboratory tests may measure either the total hormone or free hormone (not bound to protein)
Learn more about laboratory testing
REFERENCE INTERVALS FOR ADULTS: FT3: 1.71-3.71 pg/ml FT4: 0.70-1.48 ng/dl.
INCREASE IN: Hyperthyroidism
DECREASE IN: Hypothyroidism