What is the Triiodothyronine, serum (T3)? Why is the test done? Everything around this, that you should know, in this post and of course our doctors are always there to help you. Just fill in your details in the form down below and we will answer all your questions for FREE!

What is the triiodothyronine(T3) test?

This test is used to measure the amount of triiodothyronine (T3) present in the blood.

Also Read: Thyroid Function Test

What is triiodothyronine(T3)?

It is one of the two hormones made by the thyroid gland (a butterfly-shaped gland near the throat). The other hormone is thyroxine (T4) which acts as a precursor to T3. T3 and T4 together are responsible for the regulation of heartbeat, metabolism, and body temperature.

The T3 hormone is present in two forms:

T3 bound: It is the most common form of T3, which is bounded to protein. Almost 99% of the total T3 present in the blood is found in this form.

T3 free: It is the active form of T3 which is not attached to anything and accounts for 0.3% of the total T3 present in the blood. It is responsible for the biological effects of T3.

This test measures both the forms of T3 (bound and free) present in the blood.

What is the normal range of T3 in the blood?

The units of measurement are ng/dl. The normal range of T3 is:

• 0-5 days: 80-200 ng/dl
• 6 days – 2 months: 80-275 ng/dl
• 3-11 months: 86-265 ng/dl
• 1 year – 5 years: 92-248 ng/dl
• 6 years -10 years: 93-231 ng/dl
• 11 years – 19 years: 91-218 ng/dl
• Above 20 years: 80-200 ng/dl

What is it used for?

This test helps:

• In diagnosing hyperthyroidism (high T3)
• In monitoring other thyroid disorders when done with T4 and TSH
• In monitoring the treatment for thyroid disease.

Why is this test done?

You should get it done if you’re having symptoms of hyperthyroidism, such as:

• Weight loss
• Trembling of hands
• Anxiety
• Increased heartbeat
• Bulging of eyes
• Fatigue
• Sleep disturbed
• Frequent bowel movements
• Low heat intolerance

What does it mean to have high T3 serum?

If your T3 levels are higher than the normal range, it indicates the following conditions:

• Hyperthyroidism – a condition where the thyroid gland makes much of T3.
• Thyroid hormone resistance syndrome
• Euthyroid hyperthyroxinemia
• Triiodothyronine toxicosis
• Acute thyroiditis
• Pregnancy
• Drugs that increase TBG

What does it mean to have low T3 serum?

If your T3 levels are low than the normal range, it indicates the following conditions:

• Hypothyroidism
• Subacute thyroiditis
• Chronic thyroiditis
• Nephrotic syndrome
• Drugs that decrease TBG

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For more information, you can visit Healthline and Testing.com.