Tri Iodothyronine (T3) Test: What It Is, Need, Preparation & Result

What is Tri Iodothyronine (T3) Test?

T3 or triiodothyronine test is routinely used to diagnose thyroid conditions, primarily hyperthyroidism.

The thyroid is a butterfly-shaped gland in the front of the neck and is an integral part of the endocrine system. The thyroid produces two main hormones– T3(triiodothyronine) and T4(thyroxine).

T3 is available in two forms–

• Free T3: T3 that is found floating freely in the blood and enters the tissues where it is needed.
• Bound T3: This form of T3 attaches to proteins, preventing it from entering body tissues.

A blood test that measures free and bound T3 is called a total T3 test. Depending upon what your doctor wants to measure, they will prescribe a T3 test accordingly. Your doctor may also prescribe additional thyroid tests to evaluate the health and functioning of the gland, along with a T3 test.

The T3 test is also called by several other names, such as:

• Thyroid function test
• Total triiodothyronine
• Free triiodothyronine
• FT3

Tests for free T3 as well as total T3 are used to determine thyroid health. Free and total T3 tests, along with others that evaluate thyroid function, can help determine whether a patient has an overactive versus underactive thyroid, how severe their issue is, whether they have a pituitary gland disorder, and how well treatment is working.

If a patient's TSH test is abnormal, a T3 test may be ordered as a follow-up. Thyroid panels, which include both the free and total T3 tests, are commonly used to assess thyroid function. Thyroid replacement therapy efficacy may be evaluated by FreeT3 testing. Furthermore, it can be used to detect anomalies in the proteins which bind thyroid hormones, which can aid in making a correct diagnosis.

What is Tested in Free Tri Iodothyronine (T3) Testing?

T3 (triiodothyronine) is a form of thyroid hormone that has important physiological effects. Like its counterpart T4, T3 controls metabolism, stimulates cell activity and allows for the proper operation of the body's most important organs.

T3 refers to triiodothyronine, a thyroxine hormone with three iodine atoms attached. Thyroxine (T4), is the other primary thyroid hormone. It contains four iodine atoms. The thyroid produces a few of the T3 that is in your bloodstream. However, the vast majority of T3 is produced when T4 undergoes iodine elimination in the bloodstream to become T3.

The T3 in your bloodstream is coupled to proteins for the most part (almost 99%). Of the total amount of T3, a small fraction is free T3 since it does not bind to proteins. When introduced into cells, only free T3 can trigger a wide variety of physical processes. To maintain optimal health, the body maintains a delicate balance between the levels of bound and free T3.

There are two types of T3 measurements: Total, which includes bound T3, and Free, which excludes it. Measuring T3 is one way to assess thyroid health alongside the more common TSH as well as free & total T4 testing.

Why Do You Need a T3 Test?

A T3 test is performed to check thyroid function. Thyroid function is determined by measuring T3 and T4 hormones in the blood. The T3 test measures the amount of T3 attached to proteins and floating in the blood (free T3).

Your doctor may recommend a T3 test if you show signs of a thyroid disorder, such as:

• Hypopituitarism
• Overactive thyroid
• Underactive thyroid
• If you are taking medications for hypothyroidism

When Do You Need a T3 Test?

You may need a T3 test if you show symptoms of hyperthyroidism, such as:

• Weight loss
• Anxiety
• Tremors in your hands
• Increased heart rate
• Bulging eyes
• Difficulty in sleeping
• Increased fatigue
• Increased frequency of bowel movements
• Feeling excessively hot
• Dry skin
• Hair loss

Thyroid changes are common during pregnancy, and since they are not serious, most pregnant women do not require a T3 test. However, your doctor may recommend a T3 test during pregnancy if you show the following:

• Symptoms of thyroid disease
• Have a history of thyroid disease
• Have an autoimmune condition
• Have a family history of thyroid disease

Once a T3 Test Has Begun, What Can We Expect to Happen?

The Free T3 test process is quite simple. A tiny needle will be used to extract blood from just a vein in the arm by a medical practitioner. After the vein is punctured, blood is drawn into a tiny vial or test tube. The prick of the needle entering or leaving your skin is to be expected. The average time required for this is under five minutes.

Preparation for the test: To do a T3 blood test, you won't need to do anything out of the ordinary. Should you need to discontinue the use of any medications before your examination, your doctor will advise you. The amounts of T3 in your body might be altered by the medications you take. Because some medicines can alter T3 test results, it's crucial to share your full drug list with your doctor. Your doctor will be better able to advise you on how to handle the situation if they are aware of any medications you are currently taking. Hormone-containing medications, like birth control pills and steroids, can alter your T3 levels, as can therapies that target the thyroid.

Associated risks: A blood test has next to no risk and oftentimes none at all. Minor soreness or bruise at the injection site is to be expected, although these side effects usually subside quickly.

How Do You Prepare for the T3 Test?

You don't need any special preparation for a T3 blood test. Your doctor will inform you if you need to stop taking any medications before the test, as some drugs tend to lower T3 levels.

A few drugs that may affect T3 levels in the blood include:

• Thyroid medications
• Steroids
• Birth control pills
• Hormonal pills that contain oestrogens or androgens

What Happens During a T3 Test?

During a T3 test, the phlebotomist will take a blood sample from a vein in the arm using a small needle attached to a syringe or a vial. The blood sample collected is sent for analysis. The procedure takes less than five minutes to complete.

After your blood sample has been collected, it is sent to a laboratory for testing. Once your results arrive, your doctor will share them with you and suggest the next steps.

Are There Risks of a T3 Test?

There is minimal risk involved during sample collection for a T3 test. Obtaining a proper blood sample may vary in people; a few risks associated with the withdrawal of blood for the T3 test include:

• Excessive bleeding
• Fainting or dizziness
• Bruising under the skin (hematoma)
• Infection of the skin at the site of needle prick

Understanding The Results of Tri Iodothyronine (T3) Test

You may have hyperthyroidism if your test results show an elevated total T3 or free T3. Hypothyroidism, in which the thyroid gland does not produce enough of the hormone, can manifest itself in low T3 levels.

T3 Normal Range

Different labs may report slightly different normal value ranges. The measurements and samples used in some laboratories may vary from those in others. If you have questions about the significance of your test findings, consult your healthcare professional. T3 level normalisation varies with age. In general, healthy people's normal T3 ranges are as follows:

·         Children aged one to five years: 106 - 203 nanograms per decilitre (ng/dL).

·         Children aged 6 to 10 years: 104 to 183 ng/dL.

·         Children aged 11 to 14: 68 - 186 ng/dL in

·         Adolescents aged 15 to 17: 71 - 175 ng/dL.

·         Adults aged 18 to 99 years: 79 - 165 ng/dL.

Normal free T3 levels

Free T3 test levels can be tested. In general, healthy people's normal free T3 ranges are as follows:

·         Infants till 3 days old: 1.4 - 5.4 picograms per milliliter (pg./mL)

·         Infants aged 4 to 30 days: 2.0 - 5.2 pg./mL.

·         Babies aged one month to one year: 1.5 - 6.4 pg./mL.

·         Children aged 1 to 6 years: 2.0 - 6.0 pg./mL.

·         Children aged 7 to 11: 2.7 - 5.2 pg./mL.

·         Children aged 12 to 17: 2.3 - 5.0 pg./mL in

·         Adults aged 18 to 99: 2.3 - 4.1 pg./mL.

For those under the age of 20, the Free T3 normal range has a separate set of numbers. If you want to know about your outcomes, talk to your doctor.

Exactly What Is Meant by Abnormal Outcomes

T3 levels that are abnormally high may indicate:

• An overactive thyroid (e.g., Graves’ disease), Thyrotoxicosis type 3 (rare)
• Nodulocystic toxic goiter (rare)
• The use of thyroid medication or specific nutritional aids (common)

Note that T3 levels can rise when pregnant women have morning sickness near the finish of the first trimester, when women take birth control pills, or when women take estrogen. The reasons for a lower-than-average count include:

• Serious, temporary, or even chronic disease

• Inflammation of the thyroid gland (thyroiditis) (swelling of the thyroid gland — Hashimoto disease is the most common type)

Always Get Your Doctor’s Consultation

To summarise, T3, or triiodothyronine, is a hormone produced by the thyroid gland. The T3 blood test assists a clinician in determining thyroid disorders. Free T3 Test readings that are too high or too low may reflect an overactive/underactive thyroid. Thyroid disease can be diagnosed by comparing T3 test results against T4 and TSH test findings. We hope that this blog has helped explain the process to you with clarity. For more information related to your condition, be sure to consult your physician to know if you need the test.