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Thyroid Function Tests: Procedure, Types, and Results

Image of blood sample test tubes for thyroid hormonal examination
Anderson Team
December 22, 2022
Est. Reading: 5 minutes

Tests done to measure the functionality of the thyroid gland is known as thyroid function test. The thyroid gland is located right at the front of the neck in its lower region. It is used to regulate various body functions like energy generation, mood, and body metabolism. Anderson Diagnostics is the best diagnostic centre in Chennai, providing all kinds of thyroid tests under the guidance of well-experienced lab technicians. Let us discuss the types of thyroid tests and how to understand the test results here in this blog. But before that, let’s head to the basics.

A Brief About Thyroid Gland

The thyroid gland produces Thyroxine(T4) and Triiodothyronine(T3), two major hormones secreted into the bloodstream. These hormones are transferred to every single tissue of the human system. T4 and T3 secretions are regulated by the gland called the pituitary, which is present below the brain. If these hormones' levels drop below normal, the pituitary gland immediately reacts and secretes TSH (thyroid-stimulating hormone), which makes the thyroid gland produce more amounts of T4.

In contrast, if the thyroid hormone level increases above the normal limit, the pituitary gland makes the thyroid gland secretes less T4 by stopping the production of TSH. When the system secretes abnormal levels of the thyroid hormones, the person will experience a lack of energy, high anxiety level, weight gain, depression, or weight loss. If your physician doubts that your your thyroid hormone level might be fluctuating, they might request you to do a comprehensive screening test. You should get a blood test done to check your thyroid levels if you have the following:

  • Neck swelling
  • Fast or irregular heart rate
  • High cholesterol (causing atherosclerosis due to high levels fat in the heart's arteries)
  • Abnormal menstrual cycles
  • Low libido
  • Recurrent miscarriage
  • Fertility issues
  • Osteoporosis
  • Autoimmune disorders like vitiligo or type 1 diabetes that runs in the family
  • Other symptoms of under or overactive thyroid

Besides, any of the above symptoms, if you planning to get pregnant and the family has a history of thyroid disorders, you must get a thyroid test done.

Different Types of Common Thyroid Function Tests

The common thyroid function tests are elaborated below.

Non-blood Tests

The non-blood tests are followed after blood tests. If you have an overactive thyroid, you will be recommended to take up the tests mentioned below.

  • Ultrasound Examination - An ultrasound scan detects nodules or abnormal thyroid gland enlargement. It also guides the biopsies for affected nodules. When the results are normal, the patient will be prescribed medications to regulate thyroid activity. However, they will be asked to go in for a few more tests that will check the structure of the thyroid gland, determine whether there are any tumours and if the gland is functioning properly.
  • Scans Using Technetium or Radioactive Iodine - This scan determines the cause of improper thyroid functioning. This test is crucial to decide whether the patient will require a partial or total thyroidectomy.

Blood Tests

Blood tests are done to measure the hormones T3, T4, and TSH.

  • TSH Test- This is the first hormone that will be measured to check whether the thyroid gland is functioning properly. A change in thyroid stimulating hormone level is always considered an early sign of actual damage to thyroid functioning.
  • T4 Test- T4 levels are measured if TSH is high. The active portion of T4 is called FT4. If the TSH level is elevated and the FT4 level is low, the patient is said to have hypothyroidism.
  • T3 Test- This test helps in diagnosing hyperthyroidism. Patients with elevated levels of T3 are further checked for the severity of hyperthyroidism.
  • Thyroglobulin- Tg or Thyroglobulin is a protein secreted by the thyroid cancer cells. This test is done on patients with thyroid cancer who have recently undergone surgery. It does not diagnose cancer but monitors and measures thyroid function.

Procedure for Thyroid Blood Test

A blood test for thyroid is just like any other regular lab test, which will not hinder you from performing your daily chores immediately. The technician draws a sample of blood which is called venipuncture. It is performed at a lab where the technician secures a band tightly near the vein from which the blood will be drawn. By doing so, the vein swells with blood making it easy for the person to insert the needle and collect it. The blood sample is dropped into test tubes and sent for lab analysis.

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An Elaborate Explanation on Understanding Thyroid Test Results

The way a patient feels is the best way to diagnose the severity of the thyroid disorder. A physician will be able to interpret the test results by analysing the patient's symptoms and then suggest ways to treat them. You will be requested to take additional tests if your hormone levels fall below the normal range.

The TSH has to be between 0.4 to 4.0 milli-international units for one liter of blood(mIU/L). If the TSH level is high with the FT4 in the lower range, the patient is said to have hypothyroidism. On the other hand, if the TSH level falls below the normal range and FT4 is high, then the patient will have hyperthyroidism, also called overactive thyroid. Mild thyroid failure or subclinical hypothyroidism is a condition where the TSH level is a bit high, and FT4 falls in the normal range.

When patients or pregnant women have TSH levels beyond 10mU/I with subclinical hypothyroidism, they will benefit from levothyroxine treatment. Congenital hypothyroidism occurs in babies and may lead to developmental disabilities when untreated. Therefore, newborns are routinely tested to measure the TSH and T4 levels to check whether their thyroid glands are functioning properly.

If T4 levels are high, T3 levels are further measured. High T3 levels may lead to a condition known as Grave's disease. It is associated with hyperthyroidism and is an autoimmune disorder with abnormally high ranges of T3. Diagnosing autoimmune thyroid diseases is possible with antibody tests. Some are tested positive in more than one thyroid antibody test. These positive antibodies will sometimes be found in patients even without thyroid disorders.

Factors That Influence Thyroid Function Test Results

Illnesses and medications can affect the thyroid function test results. Some of the most common factors are:

  • Medications to treat thyroid problems.
  • Serious health issues like liver disease, kidney failure, heart attack, trauma, infection, etc.
  • Steroid hormones, contraceptive pills, anti-inflammatory drugs, anticonvulsants, amiodarone (for regularizing heartbeats), lithium (for mental disorders), and vitamin or mineral supplements (when it contains biotin or iodine).

Closure

Although various methods exist to diagnose thyroid disorders, blood tests are the most precise. Thyroid disorder is hereditary, and if your family members have a history of thyroid problems, stay cautious and always consult a general physician if you experience any related symptoms. Anderson Diagnostics is the best diagnostic centre in Chennai if you want to get your thyroid levels tested with world-class standards.

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