Thyroid Profile Total (T3, T4 & TSH)
Understanding Thyroid Profile Total (T3, T4 & TSH)
What is Thyroid Profile Total (T3, T4 & TSH)?
A Thyroid Profile Total (T3, T4 & TSH) offers a series of blood tests that measure the levels of thyroid hormones in the blood. Together, these tests help identify how well your thyroid gland works. It includes tests for thyroid-stimulating hormone (TSH), thyroxine hormone (T4)- total, and triiodothyronine hormone (T3)- total.
The thyroid gland is a butterfly-shaped organ located in the neck and produces hormones like thyroxine (T4) and triiodothyronine (T3), which regulate 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.
A Thyroid Profile Total (T3, T4 & TSH) assesses the health of your thyroid gland and aids 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. This test is also recommended for women during pregnancy to check if they have adequate amounts of thyroid hormones, as these hormones are necessary for the healthy development of babies.
No special preparations are needed for this test. Usually, you do not need to stop taking your thyroid medication before taking this test. However, inform your doctor about all your medicines, as some can affect thyroid function. Biotin (Vitamin B7) is a commonly taken over-the-counter supplement that can lead to some aberrancy in your thyroid function test results even when the values are normal. Therefore, avoid taking biotin two days before this test.
Test result ranges are approximate and may differ slightly between labs depending on the methodology and laboratory guidelines. The test results will help your 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 Total (T3, T4 & TSH) used for?
A Thyroid Profile Total (T3, T4 & TSH) is done:
- As part of routine checkups to monitor your overall health.
- To evaluate symptoms 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 the treatment response of disorders like thyroid nodules and pituitary or hypothalamus gland disorders.
What does Thyroid Profile Total (T3, T4 & TSH) measure?
Contains 3 testsA Thyroid Profile Total (T3, T4 & TSH) measures the levels of three hormones in the blood, namely triiodothyronine hormone (T3) total, thyroxine hormone (T4) total, and thyroid-stimulating hormone (TSH). T3 and T4 are thyroid hormones that help regulate metabolism and energy levels in the body. On the other hand, TSH is produced by the pituitary gland and stimulates the thyroid gland to produce T3 and T4 hormones. The serum levels of the thyroid hormones and TSH have an inverse relationship, i.e., low T4 (as observed in hypothyroidism) and high T4 (as seen in hyperthyroidism) levels are associated with high and low TSH levels, respectively.
Triiodothyronine Total
A Triiodothyronine Total measures triiodothyronine, also known as T3, hormone that is produced by the thyroid gland. T3 hormone plays an important 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. Free T3 is not bound to proteins in the blood and is the active form of T3. Whereas, bound T3 is bound to proteins, such as albumin and thyroid hormone binding globulin (THBG), which prevent it from entering the body tissues.
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Thyroxine - Total
A Thyroxine - Total measures both the bound and unbound/free form of thyroxine (T4) hormone in the blood. T4 exists in the blood in two forms: bound (attached to proteins) and free (not attached to proteins). Most of the T4 circulating in the blood is bound to proteins and only a small part is free. It is necessary to maintain a fine balance of these forms to ensure the proper functioning of the body.
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Interpreting Thyroid Profile Total (T3, T4 & TSH) results
Interpretations
T3 (Triiodothyronine), Total Reference Range(s)
|
<1 Month |
Not Established |
||
|
1-23 Months |
117-239 ng/dL |
||
|
2-12 Years |
105-207 ng/dL |
||
|
13-20 Years |
86-192 ng/dL |
||
|
>20 Years |
76-181 ng/dL |
||
|
T4 (Thyroxine), Total |
4.5-12.0 mcg/dL |
|
Thyroid Stimulating Hormone (TSH) Reference Range(s)
|
Premature Infants (28-36 Weeks) |
|
|
1st Week of Life |
0.20-27.90 mIU/L |
|
Term Infants (>37 Weeks) |
|
|
Serum or Cord Blood |
1.00-39.00 mIU/L |
|
1-2 Days |
3.20-34.60 mIU/L |
|
3-4 Days |
0.70-15.40 mIU/L |
|
5 Days-4 Weeks |
1.70-9.10 mIU/L |
|
1-11 Months |
0.80-8.20 mIU/L |
|
1-19 Years |
0.50-4.30 mIU/L |
|
≥20 Years |
0.40-4.50 mIU/L |
|
Pregnancy |
|
|
First Trimester |
0.26-2.66 mIU/L |
|
Second Trimester |
0.55-2.73 mIU/L |
|
Third Trimester |
0.43-2.91 mIU/L |
Table 1. Interpretation of the Thyroid Profile Test results
|
TSH |
T4 |
T3 |
INTERPRETATION |
|
Elevated |
Normal |
Normal |
Mild (subclinical) hypothyroidism |
|
Elevated |
Low |
Low or normal |
Hypothyroidism |
|
Low |
Normal |
Normal |
Mild (subclinical) hyperthyroidism |
|
Low |
Elevated or normal |
High or normal |
Hyperthyroidism |
|
Low |
Low or normal |
Low or normal |
Nonthyroidal illness; hypothyroidism due to the disease involving the pituitary gland |
|
Normal |
Elevated |
Elevated |
Thyroid hormone resistance (Impaired sensitivity to thyroid hormone) |
- Low T4 and T3, along with high TSH level, indicates hypothyroidism. The most common cause of hypothyroidism is Hashimoto thyroiditis
- High T4 and T3, along with low TSH, indicate hyperthyroidism. The most common cause of hyperthyroidism is Grave’s disease
- Normal thyroxine (T4) and T3, along with high TSH, usually indicate mild or subclinical hypothyroidism
- 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 are at a low between 6-10 pm.
Reference Range(s) may vary from lab to lab.
Answers to Patient Concerns & Frequently Asked Questions (FAQs) about Thyroid Profile Total (T3, T4 & TSH)
Frequently Asked Questions about Thyroid Profile Total (T3, T4 & TSH)
Q. Why is a Thyroid Profile Total (T3, T4 & TSH) performed?
Q. Is fasting required for a Thyroid Profile Total (T3, T4 & TSH)?
Q. Can I take a Thyroid Profile Total (T3, T4 & TSH) during pregnancy?
Q. Is there any risk associated with this test?
Q. What are the symptoms of thyroid disorders?
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References
- Thyroid Function Tests [Internet]. Alexandria, VA: American Thyroid Association; [Accessed 07 Feb. 2023]. Available from: https://www.thyroid.org/thyroid-function-tests/
- British Thyroid Foundation. Thyroid Function Test [Internet]. Scotland: British Thyroid Foundation; 2021 [Accessed 07 Feb. 2023]. Available from: https://www.btf-thyroid.org/thyroid-function-tests
- KidsHealth. Thyroid Tests [Internet]. The Nemours Foundation; 2018 July. [Accessed 07 Feb. 2023]. https://kidshealth.org/en/parents/thyroid-tests.html
- National Institute of Diabetes and Digestive and Kidney Diseases. Thyroid Tests [Internet]. National Institute of Health; May 2017 [Accessed 07 Feb. 2023]. Available from: https://www.niddk.nih.gov/health-information/diagnostic-tests/thyroid
- Adhimoolam M, Arulmozhi R. Effect of antiepileptic drug therapy on thyroid hormones among adult epileptic patients: An analytical cross-sectional study. J Res Pharm Pract. 2016 Jul-Sep;5(3):171-4. [Accessed 07 Jul. 2023]. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4966235/
- 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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