Total T4
Total T4
Total T4 test is used to measure the thyroxine (T4) levels in your blood. The thyroid gland in your body produces this hormone. Thyroid is a butterfly-shaped gland that is located above the collarbones, close to the base of the throat.
TSH, or thyroid-stimulating hormone, causes the thyroid gland to produce T4. The body contains T4 in two different forms: free T4 and bound T4. Free T4 is used by the body tissues whereas bound T4 is attached to proteins that prevent it from entering body tissues. More than 99% of T4 is present in the bound form.
T3 and T4 play a vital role in regulating how your body stores and uses energy (metabolism). The thyroid hormones also assist in regulating a number of other body functions such as heart function, brain development, etc. Thus, getting your Total T4 test done is recommended to evaluate the thyroid gland function and to diagnose thyroid diseases
Symptoms of an overactive thyroid
Anxiety
Difficulty in sleeping
Tiredness
Sensitivity to heat
Diarrhea
Persistent thirst
Itchiness
Symptoms of an underactive thyroid
Tiredness
Sensitivity to cold
Weight gain
Constipation
Depression
Muscle aches and weakness
A Total T4 test is recommended for:
Women of all ages. Women are more likely than men to have low thyroid hormone levels
Checking how well the thyroid gland is working
Diagnosing thyroid disorders such as hyperthyroidism and hypothyroidism
Test preparation
No special preparation is required for this test. Ensure your doctor is aware of what prescription drugs, over-the-counter medicines, or dietary supplements you are taking. Ask your doctor for details about pre-test preparations, and make sure to follow instructions closely
Interpretation of the Test Results
The unit of measurement for the results are in Microgram Per Milliliter (ug/mL)
|
T4 (Thyroxine), Total |
Normal levels |
|
15-30 days
|
Not established |
|
1-4 months
|
7.20-14.40 ug/mL |
|
4-12 months
|
7.80-16.50 ug/mL |
|
1-5 years
|
7.30-15.00 ug/mL |
|
5-10 years
|
6.40-13.30 ug/mL |
|
10-15 years |
5.60-11.70 ug/mL |
|
> 15 years |
5.01-12.45 ug/mL |
Deviation from normal levels indicate the following:
· Lower than normal T4 levels may be due to conditions such as an underactive thyroid gland (hypothyroidism), Hashimoto’s disease, malnutrition, and severe acute illness.
Higher than normal T4 levels may be due to overactive thyroid gland (hyperthyroidism), which can be caused by conditions such as Grave’s disease, toxic nodular goitre or multinodular goitre, too much iodine in the body, and taking too much thyroid hormone medicine
FAQs
How is the sample collected for a Total T4 test?
A blood sample is taken from a vein in the arm using a fine needle. This procedure typically takes no longer than five minutes
What are the risks associated with a Total T4 test?
This test involves negligible risk. There might be slight pain or tenderness around the site where the needle was inserted. Rarely, the site can become infected
What factors can affect the Total T4 test results?
Several factors including diet, certain illness, stress, and pregnancy can affect the Total T4 test results. Some medications such as birth control pills, estrogen, herbal supplements, etc. may also affect your test results
What is synthetic thyroxine
Pure synthetic thyroxine (T4) is the thyroid hormone replacement that is most frequently recommended by health care professionals to treat hypothyroidism (underactive thyroid). It may also be used to treat some types of thyroid cancer along with surgery and other treatments
What foods can impact normal thyroid function?
Goitrogen-rich foods can interfere with normal thyroid function by inhibiting your body from using iodine and can also inhibit the release of thyroid hormone from thyroid gland. Goitrogen-rich foods include soy products such as tofu and tempeh, as well as vegetables like cabbage, broccoli, kale, cauliflower, spinach and fruits like peaches, strawberries, etc
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