All You Need To Know About Thyroid Function Test

Contributed by – Healthians Team

What are Thyroid Function Tests?

Thyroid function tests are a series of blood tests which are performed to check the functioning of thyroid gland. The available tests for thyroid functioning test include T3, T3RU, T4, and TSH. Now, the question is why is thyroid Function test required. A TFT measures any abnormality in the functioning of Thyroid Gland.

Overview of thyroid gland

The thyroid gland is a butterfly-shaped gland lying in front of the windpipe (trachea), just below the voice box (larynx). The main role of thyroid in the endocrine system is to regulate the metabolism, which is the body’s ability to break down food and convert it to energy for helping to regulate many of the body’s processes; such as metabolism, energy generation, and mood.

Thyroid helps in keeping the metabolism under control via the action of thyroid hormone, which it makes by extracting iodine from the blood and incorporating it into thyroid hormones.

Hormones of thyroid

Two main hormones that the thyroid produces and releases are:

• T3 (tri-iodothyronine)
• T4 (thyroxine)

Thyroid hormone test

Thyroid hormone blood tests include:

• Total thyroxine (T4)
• Free Thyroxine (FT1 or FT4)
• Triiodothyronine(T3)
• TSH (thyroid stimulating hormone) 

Why is it done?

Thyroid tests are performed for the following reasons:

• To find out what is causing an abnormal thyroid-stimulating hormone (TSH) test
• For checking how well the treatment of thyroid disease is working.
• To screen newborns for the functioning of the thyroid gland function. A newborn can have a condition called congenital hypothyroidism, which can prevent normal growth and development and cause other severe problems, such as intellectual disability if it is not treated soon after birth.

How is the blood test performed?

• Once you have fixed an appointment, a phlebotomist from Healthians will visit your place. You will be made to sit comfortably on a chair. If wearing long sleeves, then the patient will be asked to roll up one sleeve or to remove the arm from the sleeve.
• A band of rubber will be tied tightly around the upper arm to make the veins swell with blood, and the area of the skin will be cleaned with alcohol.
• Once the appropriate vein has been found, a needle will be inserted under the skin and into the vein. You may feel a sharp prick when the needle punctures the skin. The technician will then collect blood in test tubes and send it to a laboratory for analysis.
• Once the required amount of blood is drawn, they’ll withdraw the needle and place pressure on the puncture wound until the bleeding stops.
• In the end, a small bandage will be placed over the wound.

How to prepare for the test?

They are certain medicines and even pregnancy can change the results of this test. Hence, it is always advisable to keep the doctor informed about any medication that the patient is taking and about the pregnancy, if pregnant.

If the patient is on thyroid medicines, then it is advisable to inform your doctor when you took your last dose. Your doctor may instruct you to stop taking thyroid medicines temporarily before having this test.

Results of thyroid blood test

Thyroid blood test results can confirm the presence of deficiency or an excess of thyroid hormone in the body and, therefore, be used to diagnose hypothyroidism or hyperthyroidism. Though, they do not point to a specific cause. In order to determine a cause of the thyroid abnormality, the doctor will consider the patient’s history, physical examination, and medical condition.

Reference range of thyroid blood test

Thyroid function test normal range or reference range is as follows:

A TSH reading above 2.0 miu/L is a sign of progressing hypothyroidism, secreted by pituitary gland lower levels of TSH is an indicator of overactive thyroid.

NOTE: There are many conditions that can change the thyroid hormone levels. Our in-house expert doctor team will inform the patient about any abnormal results that may be related to the current symptoms and past medical conditions.

Understanding thyroid function test

Thyroid function test interpretation can be done as follows:

High Value of Thyroid Hormones

This is caused in case of Hyperthyroidism, which can be caused by:

• Diseases of the thyroid gland, such as Graves’ disease, thyroiditis, or a goiter that contains one or more abnormal growths (nodules).
• Taking too much thyroid medicine.

Symptoms of Hyperthyroidism are:

• Anxiety
• Unplanned weight loss
• Tremors
• Diarrhoea

Low Value Of Thyroid Hormones

This is caused in case of Hypothyroidism, which can be caused by:

• Thyroid disease, such as thyroiditis
• Pituitary gland disease
• Destruction of the thyroid gland by surgery or radiation.

Symptoms of Hypothyroidism include:

• Weight gain
• Fatigue
• Depression
• Brittle hair and fingernails

If the blood test results suggest that the thyroid gland is overactive or underactive, the doctor will likely put you on medication to regulate the thyroid activity.