Free Thyroxine Index Normal Range. It is an attempt to obtain an indirect measurement of free thyroxine. The free t4 reading below 0.7 is suggestive of hypothyroidism.
Estimated t4 turnover or production rate values are 5 to 6 mg/kg/d in infants, 4 μg/kg/d at 1 to 3 years, 2 to 3 μg/kg/d at 3 to 9 years, and 1 μg/kg/d in adults. Total t3 result below a range of 80 is suggestive of hypothyroidism. It is an attempt to obtain an indirect measurement of free thyroxine.
The correlation was almost as high as that of the free thyroxine (t4) index with fr.
Thyroxine binding capacity (units are in thyroxine binding index: Value of free thyroxine index. Fti = thyroxine (t4) / thyroid binding capacity. The free thyroxine index has generally been replaced by free thyroxine in the assessment of thyroid function, but is occasionally useful when a free t4 result is suspected of being anomalous.
