Free T4 Test-Reference Range

Free T4 test, also called free thyroxine test, T4 test or thyroxine test, is very important in evaluating thyroid gland function, diagnosing thyroid disease, and monitoring effectiveness of treatment.

T4 is one of the two major hormones produced by the thyroid gland, the other major thyroid hormone is T3 (triiodothyronine). Both of them can help control the rate at which the body uses energy.

The normal ranges of free T4 of adults who are equal to or more than 20 years old are between 4.5-11.7 mcg/dl.

Values higher than 11.7 mcg/dl may indicate hyperthyroidism (symptoms include sleeping difficulties, increased heart rate, weakness, diarrhea, etc.) and can be seen in patients with acute thyroiditis.

Values lower than 4.5 mcg/dl may indicate hypothyroidism (symptoms include dry skin, weight gain, hair loss, puffy skin, menstrual irregularity in women, etc.) myxedema, cretinism, chronic thyroiditis, etc.

Keywords: Free Thyroxine; T4; Thyroxine; Free T4

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