Free thyroxine test (FT4)

free thyroxine ft4

Last Updated December 20th, 2021

What is thyroxine?

Thyroxine is one of the thyroid hormones which is secreted directly into the bloodstream by the thyroid gland. It plays a significant role in digestion, heart and muscular functioning. It consists of the major part of the content of the thyroid hormones secreted by the thyroid gland. 99% of the thyroid hormones consist of thyroxine.

Is there any alternative name for thyroxine?

Free T4, tetraiodothyronine are the two alternative names for thyroxine.

What are the functions of Thyroxine?

The thyroxine hormone content in your blood helps in the regulation of:

– Bodyweight.
– Body temperature.
Muscular functioning.
– Metabolism.
Heart rate.

What is the Free Thyroxine? 

There are two forms of thyroxine present in the human bloodstream:

– Free thyroxine.
– Bound thyroxine.

In the total T4 test, both are tested. But Free Thyroxine test is considered more accurate for the diagnosis of various thyroid disorders.

What is the Free Thyroxine Test?

The Free Thyroxine Test is used to check the free thyroxine level in the blood. It helps in evaluating the functioning of the thyroid gland.

When should I take a Free Thyroxine Test?

If there are any symptoms of hyperthyroidism and hypothyroidism noticed, Free Thyroxine Test helps in diagnosing the thyroid disorder correctly. If there is an imbalance in the TSH(Thyroid Stimulating Hormone), FT4 is tested for monitoring the exact disorder.

What are the symptoms of thyroid disorders?

Here are a few common symptoms of hyperthyroidism:

– Restlessness.
– Agitation.
– Tremors
– Weight loss despite an increased appetite.
– Sweating.
Rapid heart rate.
– Intolerance to heat.
– Frequent bowel movements.

A few common symptoms of hypothyroidism:

– Increased sensitivity to cold.
– Constipation.
– Dry skin.
– Weight gain.
– Puffy face.
– Hoarseness.
– Muscle weakness.
– Elevated blood cholesterol level.
– Muscle aches, tenderness, and stiffness.
– Pain, stiffness or swelling in your joints.
– Heavier than normal or irregular menstrual periods.

Why did my doctor recommend me a Free Thyroxine Test?

If your doctor has suggested you a Free Thyroxine Test, he suspects any of these following disorders listed below:

– Thyroid nodules.
Hashimoto’s thyroiditis.
– Hyperparathyroidism.
– Thyroid cancer.
– Thyroiditis.
– Hyperthyroidism.
– Hypothyroidism.
Graves’ disease.

Why did my doctor suggest me an FT4 Test?

For detecting any thyroid disorders, TSH(Thyroid-Stimulating Hormone) is tested initially. If any abnormality is diagnosed in TSH level, the doctor suggests a Free Thyroxine Test. 

What are the preparations needed for the test?

– No fasting is required.
– Your doctor might suggest you stop a few medications that you had already been taking.
-You might be asked to stop a few thyroid hormone medications prior to the test.

How is the Free Thyroxine Test(FT4) performed?

For the thyroxine test to be conducted. A blood sample has to be collected using the venipuncture procedure. The procedure is as follows:
– A tourniquet or an elastic band is wrapped around the upper arm.
– This makes the veins more prominent.
– A needle or syringe is injected to draw blood.
– The blood is collected in the tube of the syringe.
– The needle is pulled out and the tourniquet is removed.
– A cotton swab or bandage is put on the spot of the puncture of the vein to avoid any bleeding.
-This sample blood is then sent to the laboratories for testing.

Will I experience any pain during this test?

This test involves the collection of blood by syringe or needle. It is a safe test with no risk factors associated with it at all. But some people experience dizziness or lightheadedness after the collection of blood which is very normal.It might cause Hematoma (blood accumulating under the skin causing a lump or bruise).There might be pain associated with too many punctures for finding a vein

What is the price of the Free Thyroxine Test in India?

In India, the price for this test ranges from Rs 400 to Rs 1000. It might vary with the diagnostic centers and the city or the state it is located in.

When am I going to get the results?

The test results are given the very next day of the test itself. It can vary as well depending on the diagnostic centers, laboratories, and their locations.

How to interpret my Free Thyroxine Test Report?

The normal level of Free Thyroxine in the body of an adult is 0.8 to 2.8 nanograms per deciliter (ng/dL). If your Free Thyroxine level is more than the normal range, it may result in Hyperthyroidism whereas a lower level of Free Thyroxine Level can result in Hypothyroidism.

Is it safe to take a Free Thyroxine test during pregnancy?

Yes. It is completely safe for the mother as well as the fetus to take Free Thyroxine Test during pregnancy.

Why did my doctor recommend the Free Thyroxine Test during pregnancy?

The Free Thyroxine level is higher than the normal level during pregnancy. But the level of increase is not abrupt. If there are symptoms of hyperthyroidism noticed, the doctor recommends taking the Free Thyroxine Test to confirm hyperthyroidism. The most common symptoms of hyperthyroidism in pregnant women are:

– Fast and irregular heartbeat.
– Shaky hands.
– Unexplained weight loss or failure to have normal pregnancy weight gain.

Is it necessary to check the Free Thyroxine Level during pregnancy?

It is always suggested to take a Free Thyroxine Test during pregnancy since a higher level of Free Thyroxine (hyperthyroidism) can have adverse effects on the pregnancy which might lead to:

– Miscarriage.
– Premature birth.
– Low birth weight.
– Preeclampsia—a dangerous rise in blood pressure in late pregnancy.
Thyroid storm—a sudden, severe worsening of symptoms.
Congestive heart failure.

Therefore it’s highly necessary to go through Free Thyroxine check-up during pregnancy to cut down on any of these situations.

Is it safe to breastfeed my baby while intaking thyroid disorder medicine?

Yes, it is completely safe to breastfeed even if you are taking thyroid disorder medicines. Thyroxine plays a significant role in milk production. Thus intaking medicines and treating thyroid disorders keep the mother’s Free Thyroxine level normal helping her to breastfeed the baby with no side effects at all.

Is it safe for kids to take the Free Thyroxine test?

It’s completely safe for kids to take the FT4 Test since it just involves the collection of blood. There can be a brief tingling pain due to the pricking of the needle into the vein for the collection of the blood. This pain fades away in a few minutes or hours after the blood is collected.

When should I get the Free Thyroxine Test for my kid?

If your kid is showing any  kind of symptoms of hyperthyroidism like shortness of breath, weight loss, protruding eyes, elevated blood pressure, enlarged thyroid gland or symptoms of hypothyroidism like depression, lower heart rate, puffy face, weight gain, etc, it is highly recommended to go for a T4(Free Thyroxine) Test.

How prevalent are thyroid disorders in India?

According to various studies and reports, 42 million people in India are suffering from a thyroid disorder, including both hypothyroidism and hyperthyroidism.


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