Thyroid Function tests are a series of blood tests used to measure how well your thyroid gland is working. Available tests include T3, T3RU, T4, and TSH.
The thyroid gland processes hormones that regulate your body’s metabolism (weight, temperature, energy). Thyroid blood tests can help determine whether you have hypothyroidism (too little thyroid hormone) or hyperthyroidism (too much).
| Also Known as | TFT, Thyroid Panel, Thyroid Function Tests, Thyroid Profile, |
| Test Purpose | To measure how well your thyroid gland is working. |
| Test Preparations | No Need any Preparation for This Test |
| Test Components | T3, FT3, T4, FT4, TSH, Thyroglobulin (Tg) |
| Specimen | 2 ML (1 ML Min.) Blood From 1 SST |
| Stability Room | 2 hours |
| Stability Refrigerated | 48 hours |
| Stability Frozen | 4 Weeks |
| Method | Chemiluminescent Immunoassay (CLIA) |
| Download Report | Download Report |
| TEST | Definition |
|---|---|
| TSH | A pituitary hormone that stimulates the thyroid gland and reflects thyroid function |
| Free T4 | A thyroid hormone that does not bind to protein |
| Total T4 | A thyroid hormone that is bound to protein and not bound or free. |
| Free T3 | A thyroid hormone that does not bind to protein |
| Total T3 | A thyroid hormone that is bound to protein and not bound or free. |
| Thyroglobulin (Tg) | A protein produced by healthy thyroids and by certain thyroid cancers |
| Antibodies | What do they indicate? |
| Thyroid peroxidase antibodies (TPOAb) | Raised in Hashimoto’s thyroiditis (or autoimmune thyroiditis) and sometimes raised in Graves’ disease |
| Thyroglobulin antibodies (Tg Ab) | Sometimes raised Hashimoto’s thyroiditis |
| Thyroid stimulating hormone receptor antibodies (TSHR Ab) | Raised in Graves’ disease |
| Thyroid Stimulating Immunoglobulin (TSI) antibody | May be raised in Graves’ disease. |
Definations of Thyroid Functions Tests
T3:
The Total T3 test measures the bound(T3) and free forms of T3(FreeT3) levels in the blood to evaluate the thyroid functioning if it has underactive(Hypothyroidism) or overactive(Hyperthyroidism) performance.
Free T3:
Free Triiodothyronine test measures the amount of T3 in the blood. Blood levels of T3 are higher or lower because of inadequate or uncontrolled production of the hormone by the thyroid gland because of thyroid dysfunction or pituitary dysfunction.
T3 Uptake:
The T3 uptake test, also called the T3 resin uptake (T3RU) test, indirectly measures the binding capacity of thyroxine binding globulin TBG. It does not measure T3, despite the name
T3RU:
The T3 uptake test, also called the T3 resin uptake test, indirectly measures the binding capacity of TBG. Does not measure T3, despite the name.
T4:
T4: This Test measure free and bound T4 together. A calculation can be done to find out how much T4 is free. This is a less accurate way to check how well your thyroid is working.
Free T4:
Free T4: It directly measures the amount of free T4 in the blood. Medical experts believe that this test provides more accurate information than a total T4 test, which is why it is used more often.
Free T4 Index:
Free T4 Index (FTI): Estimating the amount of circulating FT4 using the Total T4 and thyroid binding capacity (TBC).
TSH :
TSH produced by the pituitary. TSH Test stimulates the release of thyroid hormone from thyroglobulin. It also stimulates the growth of thyroid follicular cells. An abnormal level of TSH Test can mean that the thyroid hormone regulation system is out of whack, usually as a result of a benign condition (Hyperthyroidismor Hypothyroidism).
Thyroid peroxidase antibodies (TPOAb):
Thyroid peroxidase is a crucial enzyme for the production of thyroid hormones. TPOAb can interfere with the action of this enzyme. Almost all patients with Hashimoto’s thyroiditis have elevated levels of TPOAb.
Thyroglobulin Antibodies (TgAb):
Thyroglobulin is a protein produced by the thyroid gland. TgAb may be present when the thyroid has been damaged. Thyroglobulin antibodies are often measured in addition to thyroglobulin tests after a patient completes treatment for thyroid cancer.
Thyroid stimulating hormone receptor antibodies (TSHR Ab):
TRAbs are antibodies that bind to receptors on thyroid cells normally activated by thyroid-stimulating hormone (TSH). In Graves’ disease, an antibody called thyroid-stimulating immunoglobulin (TSI) binds to the TSH receptor and mimics the action of TSH. This causes constant stimulation of the thyroid gland, causing it to release too much thyroid hormone into the bloodstream. TSI stimulation can also cause abnormal growth of the thyroid gland.
Thyroid Stimulating Immunoglobulin (TSI) antibody:
TSIs are antibodies that signal the thyroid gland to become more active and release excessive amounts of thyroid hormone into the blood. A TSI test measures the amount of thyroid-stimulating immunoglobulin in the blood.
Why get Tested :
Various blood tests can be used to find out if your thyroid gland is working normally. These thyroid function tests reveal whether your thyroid is making the right amount of thyroid hormones. Thyroid blood tests may be ordered:
- To check for thyroid disease before it causes symptoms, especially in newborns
- To diagnose an underactive or overactive thyroid
- To determine if an underlying disorder, such as Hashimoto’s thyroiditis, Graves’ disease, or thyroid inflammation, may be causing an underactive or overactive thyroid
- To evaluate a lump in the thyroid gland, called a thyroid nodule
- To evaluate an enlarged thyroid gland, called a goiter
- To monitor the treatment of thyroid disorders
When to Get Tested:
You should make an appointment with your Doctor and request a blood test if you have:
- Symptoms of an overactive or underactive thyroid
- Swelling or thickening in the neck
- An irregular or fast heart rate
- High cholesterol (which causes atherosclerosis, a buildup of fat in the arteries)
- Osteoporosis (brittle or thinned bones)
- Fertility problems, abnormal menstrual cycles, recurrent miscarriage, low libido
- Family history of autoimmune disorders, eg type 1 diabetes, vitiligo, etc.
or if you are
- Feeling bad after having a baby
- Pregnancy planning or early pregnancy (and you have a family or personal history of thyroid disorders, a history of postpartum thyroiditis, or type 1 diabetes)
Sample Required
2 ml Blood in SST
Sample Precations:
No Need any Preparation
Normal values:
T3 , Free T3, T4 Uptake
- Total T3 : 0.7 to 2.0 nmol/L
- Free T3 : 2.0 to 7.0 pmol/L
- T3 Uptake: 25 – 50 %
See More Values Click Here
T4, Ftee T4, Free T4 Index:
- T4: 5.0 μg/dl – 12.0 μg/dl
- FT4: 0.8 ng/dl – 1.8 ng/dl
- FT4I: 6.0 mcg/dL –11.0 mcg/dL
See More Values Click Here
TSH
- Male: 0.3 – 5.0 uIU/ml
- Non Pregnant: 0.3 – 5.0 uIU/ml
- Pregnant:
- First trimester: 0.1 to 2.5 mIU/ml
- Second trimester: 0.2 to 3.0 mIU/ml
- Third timester: 0.3 to 3.0 mIU/ml
See More Values Click Here
What other tests might I have along with this test?
You may also need these tests:
- T3 uptake.
- Free T3.
- Total T3.
- Total T4.
- Free T4.
- Free thyroxine index.
- TSH.
- Thyroglobulin (Tg)
- Thyroid scan
- Radioactive iodine uptake test
- Thyroid-stimulating immunoglobulin (TSI) test
Thyroid Function Tests Summary:
| Disease | T3 | T4 (total) | T4 free | TSH | Cholesterol |
|---|---|---|---|---|---|
| Hypothyroidism, | decreased | decreased | low | increased | increased |
| Hyperthyroidism | increased | increased | increased | decreased or absent | decreased |
| Excess Thyroid binding globulin (TBG) | increased | increased | Normal | decreased | |
| Decreased thyroglobulin (TBG) | Low | Low | Normal |
| TSH | Total and Free T4 | Total and Free T3 | MOST LIKELY DIAGNOSIS |
|---|---|---|---|
| Normal | Normal | Normal | Normal thyroid function (e.g., “euthyroid”) |
| Normal or decreased | Normal or decreased | Decreased | Normal adjustment in thyroid function due to illness (nonthyroidal illness or sick euthyroid syndrome) |
| Increased | Normal | Normal | Subclinical hypothyroidism; in a person with hypothyroidism on treatment, not enough thyroid hormone is being given |
| Increased | Decreased | Normal of decreased | Hypothyroidism resulting from a problem with the thyroid gland itself (primary hypothyroidism) |
| Normal or increased | Increased | Increased | Hyperthyroidism resulting from a problem with the pituitary gland signals (central hyperthyroidism) or from a problem with the thyroid hormone receptor (thyroid hormone resistance) |
| Decreased | Normal | Normal | Subclinical Hyperthyroidism; in a person with Hypothyroidism, too much thyroid hormone is being given |
| Decreased | Normal | Increased | Hyperthyroidism resulting from the thyroid gland making too much active thyroid hormone T3 (uncommon, also known as T3 toxicosis) |
| Decreased | Increased | Increased | Hyperthyroidism resulting from the gland making too much thyroid hormones (primary hyperthyroidism) |
| Decreased | Decreased | Decreased | Hypothyroidism resulting from a problem with the hypothalamus or pituitary signals that govern the thyroid gland (central hypothyroidism) |
FAQs
Q: What does the thyroid function test detect?
A: Thyroid function tests are used to detect a number of thyroid problems. The tests measure the amount of different hormones, including thyroid-stimulating hormone (TSH), thyroxine (T4), and triiodothyronine (T3). Other tests on the thyroid include various antibodies related to thyroid tissue.
Q: What are the 3 thyroid tests?
A: Commonly ordered thyroid blood tests include:
- T4 test: This is done to measure the blood level of the hormone T4 (thyroxine). …
- TSH test: A thyroid-stimulating hormone (TSH) test can help find out how well your thyroid is working. …
- Total T3 test: The total T3 test measures the other important thyroid hormone in the blood.
Q: What are normal levels of thyroid function?
A:
- Total T3 : 0.7 to 2.0 nmol/L
- Free T3 : 2.0 to 7.0 pmol/L
- T3 Uptake: 25 – 50 %
- T4: 5.0 μg/dl – 12.0 μg/dl
- FT4: 0.8 ng/dl – 1.8 ng/dl
- FT4I: 6.0 mcg/dL –11.0 mcg/dL
- TSH: 0.3 – 5.0 uIU/ml
Q: What are the 5 thyroid tests?
A: Thyroid blood tests include:
- TSH: Measures Thyroid Stimulating Hormone. It is the most accurate measure of thyroid activity.
- T3 and T4: measure different thyroid hormones.
- TSI: Measures Thyroid Stimulating Immunoglobulin.
- Thyroid antibody test: Measures antibodies (markers in the blood).
Q: Is a thyroid problem serious?
A: If your body makes too much thyroid hormone, you can develop a condition called hyperthyroidism. If your body makes too little thyroid hormone, it’s called hypothyroidism. Both of these conditions are serious and must be treated by your health care provider.
Q: What are the early warning signs of thyroid problems?
A: 7 early warning signs of thyroid problems
- Fatigue.
- Weight gain.
- Weightloss.
- Slow heart rate.
- Incrise of cardiac frecuency.
- Sensitivity to heat.
- Sensitivity to cold.
Q: Which thyroid test is better?
A: TSH assessment is the single most useful test of thyroid function in the vast majority of patients. Primary care providers will rarely need to order any other biochemical thyroid tests. In most cases, the TSH will be within the normal range and no further testing is indicated.
Q: How can I improve my thyroid function?
A: Fortunately, eating the right nutrients and taking medication can help reduce symptoms and improve thyroid function. Nutrients that are great for the thyroid are iodine, selenium, and zinc. Following a thyroid-friendly diet can minimize your symptoms and help you manage your weight.
Q: What causes thyroid problems?
A: Thyroid problems can be caused by: Iodine deficiency. autoimmune diseases, in which the immune system attacks the thyroid, leading to hyperthyroidism (caused by Graves’ disease) or hypothyroidism (caused by Hashimoto’s disease), inflammation (which may or may not cause pain), and many others
Q: What is the best time for thyroid testing?
A: A morning thyroid test provides the best results | RedRiver Health and Wellness Center. If you regularly check your TSH levels to monitor the health of your thyroid, it is recommended to always do so in the morning. Otherwise, your results may show a false normal result even though you still have a low thyroid.
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