Biomarkers

What is the Free Thyroxine Index?

Free thyroxine index is considered to be a reliable indicator of thyroid status in the presence of abnormalities in plasma protein binding. The free thyroxine index has generally been replaced by Free Thyroxine in the assessment of thyroid function, but is occasionally useful when a free T4 result is suspected of being anomalous.

free thyroxine index high low meaning results thyroid t4 t3 free

Reference ranges for the free thyroxine index:

  • 0-5 days: 5.1-20.8 mcg/dL
  • 6 days-2 months: 5.5-18.0 mcg/dL
  • 3-11 months: 5.7-16.8 mcg/dL
  • 1-5 years: 5.9-15.0 mcg/dL
  • 6-10 years: 6.0-13.9 mcg/dL
  • 11-19 years: 5.9-13.2 mcg/dL
  • > or =20 years: 4.8-12.7 mcg/dL

How to calculate the free thyroxine index?

The free thyroxine index (FTI) is determined by the following calculation:

Abnormal levels:

High levels are caused by hyperthyroidism.

Low levels are caused by hypothyroidism. Low results may also occur in hospitalised patients with non-thyroidal illness.

 

One comment

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.