T3 (Total)
Triiodothyronine (T3) is one of the two main hormones the thyroid gland releases into the bloodstream. A blood test that measures both free T3 and bound T3 is called a total T3 test; a different blood test measures free T3 alone.
Why it matters: A T3 test helps diagnose thyroid conditions, particularly hyperthyroidism, helps determine how severe hyperthyroidism is, and is used to monitor T3 levels during thyroid hormone replacement therapy. Higher-than-usual T3 typically indicates hyperthyroidism, an overactive thyroid, which itself has several causes including Graves' disease, thyroid nodules and thyroiditis. Lower-than-usual T3 may indicate hypothyroidism.
Source · Cleveland Clinic — what it is, why it matters, what moves it, related conditions
May decrease with:
What is T3 (Total)?
Triiodothyronine (T3) is one of the two main hormones the thyroid gland releases into the bloodstream. A blood test that measures both free T3 and bound T3 is called a total T3 test; a different blood test measures free T3 alone.
What might a high or low T3 (Total) mean?
A T3 test helps diagnose thyroid conditions, particularly hyperthyroidism, helps determine how severe hyperthyroidism is, and is used to monitor T3 levels during thyroid hormone replacement therapy. Higher-than-usual T3 typically indicates hyperthyroidism, an overactive thyroid, which itself has several causes including Graves' disease, thyroid nodules and thyroiditis. Lower-than-usual T3 may indicate hypothyroidism.
What is the typical reference range for T3 (Total)?
The general-population reference range shown here is 1.3 – 3.1 nmol/L. Reference ranges describe the general population and are not a personal target — discuss your results with your physician.
What can affect T3 (Total)?
It may be lower with: Medicines such as steroids and amiodarone, Severe illness.
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