Free Triiodothyronine (FT3) Test

The hormones secreted by the thyroid gland play a vital role in weight management, nervous system regulation, body temperature regulation and muscular strength. These hormones also aid in regulating various metabolic processes in the body, including heart rate or blood pressure. A person might become unwell if they have too much or too little of these hormones.

The thyroid hormone is one primary hormone that has an essential role in brain development. Two thyroid hormones are active which are:

• T4, which is generated entirely by the thyroid gland.
• T3, which is created by de-iodinating T4.

T3 is one crucial hormone present in the thyroid gland. It is a tiny butterfly-shaped gland found near the throat. Thyroxine is the other hormone (T4). T3 and T4 hormones work together to control how your body uses energy.

The T3 hormones are found in two forms:

• Free T3 that is unattached to anything
• Bound T3 that is bound to proteins

Thyroid function tests diagnose a variety of thyroid conditions. Thyroid-Stimulating Hormone (TSH), Thyroxine (T4) and Triiodothyronine (T3) are among the hormones measured in the T3 test. A complete T3 test evaluates both bound and Free T3.

The pituitary gland in the brain produces TSH. Then, TSH travels through the bloodstream to the thyroid gland, located at the front of the neck. TSH then controls the amount of T4 and T3 released into the bloodstream.

The Free T3 test only evaluates free T3. T3 levels can be checked using either bound or free T3 tests. Abnormal T3 levels might indicate thyroid illness.

T3 can worsen sooner than T4 and return to standard later than T4. Hence, the free triiodothyronine (FT3) test determines whether the thyroid functions correctly or not. It mainly helps detect hyperthyroidism.

High or low Triiodothyronine levels in the body can negatively impact one's well-being and health. This is because thyroid glands can become either hyperactive or underactive. In addition, it will result in decreased or increased hormone release into the bloodstream.

When the thyroid gland produces too many hormones, it is called overactive thyroid. When the thyroid gland produces insufficient hormones, it is called the underactive thyroid. These hormone imbalances can have a variety of symptoms.

Hyperthyroidism (overactive thyroid), Hypothyroidism (underactive thyroid)

The Free T3 test measures the FT3 or free triiodothyronine hormone amounts present in the blood. The test measures:

• Low T3 levels or hypothyroidism
• High T3 levels or hyperthyroidism

Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormone. Low T3 levels might indicate hypothyroidism.

T3 levels that are too high can suggest hyperthyroidism. In addition, high T3 levels can also lead to thyrotoxicosis, which represents an excess of circulating hormones.

Thyroid cancer can produce abnormal T3 levels in rare situations. However, in most cases, this illness does not typically generate abnormal T3 levels. Because thyroid cancer and thyrotoxicosis are uncommon, hyperthyroidism is the most prevalent cause of abnormal T3 levels.

Thyroid-stimulating hormone or TSH is a test chosen for initial evaluations. A high FT4 and/or TSH result may prompt Free Triiodothyronine (FT3) measurement. Free T3 is a less reliable test for hypothyroidism. It should only be used in exceptional circumstances.

If an individual has hyperthyroidism symptoms, they may require a Free T3 test. These are some of them:

• Weight Loss
•  Fatigue
• Bulging Eyes
• Increased Heart Rate
• More Frequent Bowel Movements
•  Anxiety

If an individual has any of the following symptoms or conditions, they may require thyroid tests:

Experiencing symptoms of hypothyroidism (underactive thyroid) like

• Weight gain
• Lack of energy
• Lethargy, listlessness
• Carpal tunnel syndrome
• Obesity
• Enlarged swelling on the outer side of the neck

Experiencing symptoms of hyperthyroidism (overactive thyroid)

• Losing weight even when eating well
• Hairfall
• Swelling around eyes
• Hyperpigmented patches on the skin
• Feverish feeling through the day, regularly.

Being on a thyroid hormone replacement therapy

A woman with reproductive issues such as infertility and PCOS

In some rare cases, infants are born without a functioning thyroid gland.

During pregnancy, thyroid alterations can occur. Most pregnant women do not require T3 testing since these alterations are usually not severe.

However, the doctor may request a T3 test when you're pregnant if you have:

• Thyroid Disease Symptom
• History/ Family History of Thyroid Disease
• Auto-Immune Disease

After each dose adjustment of medication for hyperthyroid or hypothyroid, the testing of thyroid level will be done. Thyroid levels are generally only tested once a year after they are in the normal range. However, the repetition of the test at regular intervals is suggested for hypothyroid illness. The follow-up test can be taken anytime between 2 weeks and 3 months after the first test.

Before the Test

Generally, no preparation is mandated for an FT3 test. However, if this test coincides with another which requires certain measures, your healthcare provider may advise you to refrain from consuming specific food items. It is advisable to always seek guidance from your doctor prior to the test for optimal results.

During the Test

A small sample of your blood will be extracted from a vein in your arm. Here are the key aspects to anticipate during the test:

• The region where the needle will be inserted will be disinfected with an antiseptic.
• A tourniquet band will be applied to your arm to enhance vein visibility.
• A needle will be introduced into the vein to draw the blood. This may cause a brief pinching sensation lasting a few seconds.
• The blood will be collected in a vial or small test tube and the blank label will be filled with your details.

After the Test

Following the blood collection:

• A bandage will be affixed to the puncture site to prevent bleeding.
• Minor bruising is common. An uncommon effect is lightheadedness. You should sit for a few minutes if you feel dizzy.
• Contact your healthcare provider in case of bleeding, pain, or rashes at the puncture site.

The Free Triiodothyronine or Free T3 test includes the amount of active T3 forms that are not protein-bound.

FT3 - Free Triiodothyronine

The range for the Free T3 Test is measured in pg/dL. The normal range for the Free T3 test is mentioned in the table. In addition, the severity of the thyroid hormone varies according to age and gender.

The normal values and reference ranges of the test may vary from lab to lab. Please refer to the ranges mentioned in the report and consult a doctor to understand the interpretation of lab reports.

The normal range in the Free T3 test indicates that the thyroid gland is functioning well. A high free T3 level might suggest a hyperactive thyroid gland or hyperthyroidism. Low free T3 levels might indicate a thyroid gland that isn't functioning correctly or hypothyroidism. Some of these symptoms include:

• Obesity
• weight gain
• weight loss even when eating normally
• Hairfall
• Lassitude and lethargy
• Goitre
• Swelling in neck
• Dark patches on the skin
• Lack of mental alertness.a