Thyroid Profile Total (T3, T4 & TSH)
Understanding Thyroid Profile Total (T3, T4 & TSH)
What is Thyroid Profile Total (T3, T4 & TSH)?
The 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 are responsible for regulating metabolism and other bodily functions. The production and release of these hormones are controlled by the thyroid-stimulating hormone (TSH), which is produced by the pituitary gland.
The 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 any 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.
Total T3 & T4 concentrations are also altered by physiological or pathological changes in thyroxine binding globulin (TBG) capacity, TBG being the transport protein responsible for binding to and transporting thyroid hormones to the necessary tissues. TSH may show marked fluctuations in an individual due to a number of factors, one of which is the time of the day when it is measured. So, the daytime testing for TSH measurements is usually preferred.
No special preparations are needed for this profile. Usually, you do not need to stop taking your thyroid medication before taking this test. However, let your doctor know about all the medications you take as some of them can affect thyroid function.
Test result ranges are approximate and may differ slightly between different 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?
The Thyroid Profile Total (T3, T4 & TSH) is done:
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As part of routine checkups to monitor your overall health.
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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.
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To diagnose and monitor the treatment of any suspected thyroid disease, such as hypothyroidism, hyperthyroidism, Grave’s disease, thyroiditis, or Hashimoto’s disease.
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To detect an underactive thyroid gland in newborn babies.
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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 testsThe 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
The Triiodothyronine Total test 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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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.
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Thyroxine - Total
The Thyroxine - Total test 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 |
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1-23 Months |
117-239 ng/dL |
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2-12 Years |
105-207 ng/dL |
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13-20 Years |
86-192 ng/dL |
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>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) |
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1st Week of Life |
0.20-27.90 mIU/L |
Term Infants (>37 Weeks) |
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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.