Thyroid Profile Free (FT3, FT4 & TSH)
Understanding Thyroid Profile Free (FT3, FT4 & TSH)
What is Thyroid Profile Free (FT3, FT4 & TSH)?
The Thyroid Profile Free (FT3, FT4 & TSH) test offers a series of blood tests that measure the levels of free form of thyroid hormones in the blood. This test is used to identify the functioning of the thyroid gland and measure the levels of thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3).
The thyroid gland is a butterfly-shaped organ in the neck that produces hormones like thyroxine (T4) and triiodothyronine (T3), which are responsible for regulating metabolism and other bodily functions. The production and release of these hormones are controlled by the thyroid-stimulating hormone (TSH) produced by the pituitary gland. FT4 and FT3 represent the free or unbound and active forms of thyroxine and triiodothyronine, respectively. It reflects the amount of available thyroid hormone circulating in the blood.
The Thyroid Profile Free (FT3, FT4 & TSH) test is used to assess how well your thyroid gland is working and aid in the diagnosis and management of thyroid disorders, such as an overactive thyroid gland (hyperthyroidism) or an underactive thyroid gland (hypothyroidism). Your doctor may advise this test if you show symptoms suggestive of hyperthyroidism, such as weight loss, nervousness, irritability, increased sweating, and rapid heartbeat, or hypothyroidism, such as weight gain, fatigue, sensitivity to cold, constipation, and dry skin. It is also important for pregnant women to have healthy amounts of thyroid hormones to ensure the healthy development of their babies. Therefore, screening with a TFT-Free test may be recommended for pregnant women.
No special preparations are needed for the tests of this package. Usually, you do not need to stop taking your thyroid medication before taking this test. However, let your doctor know about all your medications, as some can affect thyroid function.
Test result ranges are approximate and may differ slightly between labs depending on the methodology and laboratory guidelines. The test results will help the doctor determine your medical condition, make recommendations for lifestyle modifications such as diet and exercise, decide whether or not medication will be required to manage your condition and formulate your overall treatment plan.
What is Thyroid Profile Free (FT3, FT4 & TSH) used for?
The Thyroid Profile Free (FT3, FT4 & TSH) is done:
- As part of routine health checkups to monitor your overall health.
- To evaluate symptoms that can be caused by an imbalance in thyroid hormone levels, such as fatigue, weight loss/gain, hair loss, changes to heart rate, dry skin, and sensitivity to cold.
- To diagnose and monitor the treatment of any suspected thyroid disease, such as hypothyroidism, hyperthyroidism, Grave’s disease, thyroiditis, or Hashimoto’s disease.
- To detect an underactive thyroid gland in newborn babies.
- To evaluate and monitor treatments of other disorders, such as thyroid nodules and pituitary or hypothalamus gland disorders.
- To investigate the cause of infertility.
What does Thyroid Profile Free (FT3, FT4 & TSH) measure?
Contains 3 testsThyroxine (T4) and Triiodothyronine (T3) are thyroid hormones that help regulate metabolism and energy levels. On the other hand, the pituitary gland produces thyroid-stimulating hormone (TSH) and stimulates the thyroid gland to produce T3 and T4 hormones. T3 and T4 circulate in the blood in two forms: bound (attached to proteins) and free (does not attach to any protein). The Thyroid Profile Free (FT3, FT4 & TSH) measures the free or active form of these hormones.
The serum levels of the thyroid hormones and TSH have an inverse relationship, i.e., low T4 and T3 (as observed in hypothyroidism) and high T4 and T3 (as seen in hyperthyroidism) levels are associated with high and low TSH levels, respectively.
TSH (Thyroid Stimulating Hormone) Ultrasensitive
The TSH (Thyroid Stimulating Hormone) Ultrasensitive test measures the levels of TSH hormone in the blood. TSH is produced by the pituitary gland located in the brain. Its function is to stimulate and regulate the functioning of the thyroid gland. It signals the thyroid gland to increase or decrease the production of thyroid hormones T3 and T4 (essential for regulating our body’s metabolism, temperature, heart rate, and growth) when their levels are low or high, respectively. Therefore, when the levels of T3 & T4 decrease, the pituitary gland is stimulated to release TSH. This high TSH level, in turn, stimulates the thyroid gland to release more thyroid hormones (T3 & T4); the vice-versa happens when the levels of thyroid hormones increase.
Know more about TSH (Thyroid Stimulating Hormone) Ultrasensitive
Thyroxine - Free
The Thyroxine - Free test measures the free form of thyroxine (T4) hormone made by the thyroid gland. T4 hormone exists in the blood in two forms: bound (attached to proteins) and free (not attached to proteins). Most of the T4 hormone circulating in the blood is bound to proteins and only a small part is free. A delicate balance of bound and free T4 should be maintained to ensure the proper functioning of the body.
Know more about Thyroxine - Free
Triiodothyronine Free
The Triiodothyronine Free test measures the levels of free triiodothyronine (T3), a hormone produced by the thyroid gland. T3 hormone plays a vital role in regulating the body's metabolism, energy levels, and growth & development. It exists in the blood in two forms: free T3 and bound T3. Only a small portion of T3 is free (not bound to proteins) and can be utilized by the body’s tissues. In contrast, more than 99% of T3 is bound to proteins, such as albumin and thyroid-binding globulin (TBG), preventing it from entering the tissues. The body balances bound and free T3 to ensure proper functioning.
Know more about Triiodothyronine Free
Interpreting Thyroid Profile Free (FT3, FT4 & TSH) results
Interpretations
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Low T4 and T3, along with a high TSH level, indicate hypothyroidism. The most common cause of hypothyroidism is Hashimoto thyroiditis.
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High T4 and T3, along with low TSH, indicate hyperthyroidism. The most common cause of hyperthyroidism is Graves’ disease.
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Normal thyroxine T4 and T3, along with high TSH, usually indicates mild or subclinical hypothyroidism.
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Normal T3 and T4, along with low TSH, indicate mild or subclinical hyperthyroidism.
Note: TSH levels show circadian variation (fluctuates during the 24-hour cycle), reaching peak levels between 2 - 4 am and low levels between 6-10 pm.
Answers to Patient Concerns & Frequently Asked Questions (FAQs) about Thyroid Profile Free (FT3, FT4 & TSH)
Frequently Asked Questions about Thyroid Profile Free (FT3, FT4 & TSH)
Q. What is the full form of T3, T4, and TSH?
Q. What does the Thyroid Profile Free (FT3, FT4 & TSH) measure?
Q. What is the relation between T3, T4, and TSH?
Q. Why is the Thyroid Profile Free (FT3, FT4 & TSH) performed?
Q. What is the procedure of sample collection for the Thyroid Profile Free (FT3, FT4 & TSH)?
Q. Is fasting required before the Thyroid Profile Free (FT3, FT4 & TSH)?
Q. Can I take the Thyroid Profile Free (FT3, FT4 & TSH) during pregnancy?
Q. Is there any risk associated with the Thyroid Profile Free (FT3, FT4 & TSH)?
Q. What are some of the common symptoms of thyroid disorders?
Q. Which foods/nutrients can adversely affect my thyroid gland?
Q. What additional tests can be performed along with the Thyroid Profile Free (FT3, FT4 & TSH)?
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References
- Thyroid Function Tests [Internet]. Alexandria, VA: American Thyroid Association; [Accessed 26 Jun. 2023]. Available from: https://www.thyroid.org/thyroid-function-tests/
- Thyroid Function Test [Internet]. Scotland: British Thyroid Foundation; 2021 [Accessed 26 Jun. 2023]. Available from: https://www.btf-thyroid.org/thyroid-function-tests
- Thyroid Tests [Internet]. NIDDK; May 2017 [Accessed 26 Jun. 2023]. Available from: https://www.niddk.nih.gov/health-information/diagnostic-tests/thyroid
- Thyroid Function Tests [Internet]. American Thyroid Association; 2019 [Accessed 26 Jun. 2023]. Available from: https://www.thyroid.org/wp-content/uploads/patients/brochures/thyroid_function_tests_faq.pdf
- Block-Galarza J. Thyroid Function Tests [Internet]. Alexandria, VA: American Thyroid Association. [Accessed 07 Jul. 2023]. Available from: https://www.thyroid.org/patient-thyroid-information/ct-for-patients/december-2018/vol-11-issue-12-p-3-4/#:~:text=Most%20commonly%2C%20biotin%20use%20can,hormone%20dose%20is%20too%20high
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