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Thyroxine (T4)

Thyroxine (T4) is the most common form of thyroid hormone that is released by the thyroid gland. Once it reaches the tissues, it is converted to another form of thyroid hormone called triiodothyronine (T3), which is more active in regulating the body's chemical reactions.

In tests of thyroid function, a low T4 level may indicate the presence of low thyroid levels (hypothyroidism). Certain forms of liver or kidney disease may also cause a low T4 level, even though a thyroid problem may not be present.

By Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer Matthew I. Kim, MD - Endocrinology
Current as of March 14, 2013

WebMD Medical Reference from Healthwise

Last Updated: March 14, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.