What do you know about T4 or thyroxin?

What is the T4 hormone?
The T4 or thyroxine hormone is one of the two main hormone produced in the thyroid gland. Another thyroid hormone is called T3 or triiodothyronine. These two hormone together control the body's energy levels. Almost both of these hormones bind to specific proteins in the blood. The hormone levels of these hormones are measurable and also have biological function.

When the level of the T4 hormone decreases in the bloodstream, the hypothalamus secretes the releasing hormone. This pituitary gland hormone is prepared to stimulate and secrete the TSH hormone. TSH stimulates the thyroid gland to produce more thyroid hormone T4. By increasing T4 levels, the TSH secretion decreases.

T4 accounts for about 90% of thyroid hormones. When the body needs thyroid hormone, the thyroid gland stores the stored thyroid thyroid. In the blood, the T4 hormone is free and without protein binding. Of course, all of these free T4 values ​​are 0.1% of the total T4. T4 is converted to T3 in the liver or other tissues. The free T3 is 4 to 5 times more active than the free T4. Therefore, thyroxen acts as a storage hormone. It is not able to produce energy alone.

If the thyroid gland does not produce enough T4, a person with hypothyroidism or hypothyroidism will be. Untreated hypothyroidism can lead to heart failure, seizure, and coma. In newborns, it can be delayed or slowly growing.

How is T4 tested?
In adults, blood samples are taken from a vein in the hand and in the infant with hemorrhage.

What is the purpose of the T4 test?
T4 tests may be performed with other tests, such as TSH, or sometimes with free T3 tests in the blood. This test is to:

Helping to detect low or high levels of thyroid hormones in the blood and identify the cause
Diagnosis and differentiation between various thyroid disorders
Helping to detect hormonal disorders
Helping to diagnose infertility in women
Monitoring the effectiveness of treatment in people with known thyroid disorders
Monitor the disease of people with pituitary disorders, to ensure the proper functioning of the thyroid gland, and to monitor thyroid therapies and treatments.
Monitor people with thyroid cancer that respond to TSH in tumors. The levels of the hormone TSH and T4 are regularly taken to ensure adequate levels of thyroid hormones to maintain the level of the TSH hormone without increasing T4.
What conditions can affect T4 test values?
Like the TSH test, the T4 test can also be affected by some medications.

Increase or decrease the amount of T4 binding proteins
Estrogen medications
Liver disease
Chronic Illness
Resistance to thyroid hormones
Pregnancy can increase T4 free blood levels. Although this does not mean thyroid disease.

Interpreting the results of thyroxin test
Although the values ​​of this test are different based on the laboratory kits used, reference can be made about 0.7-1.9 ng / dl for T4 free and 4-12 μg / dL for total T4.

You can simply use the membership in Trita and enter the user's area of ​​the smart doctor system, you will also be able to record the test in Trita and interpret the amount in your test without the need for a physician. Please check the blood tests section after you arrive.


  1. https://labtestsonline.org/tests/free-t4
  2. https://www.verywellhealth.com/interpret-your-thyroid-test-results-3231840


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Fatemeh Ghorbani

Fatemeh Ghorbani

فاطمه قربانی هستم، لیسانس ژنتیک، به علوم نوین پزشکی و ایمونولوژی علاقمندم. از شما دوست گرامی بخاطر مطالعه این مقاله و همچنین مجموعه تریتا بخاطر فرصت انتشار مطالبم در راستای کمک به ارتقای دانش کمال تشکر دارم. شاد باشید و سلامت

my name is Fatemeh Ghorbani, I have a B.S in genetics and interested in immunology and medical science. I believe that, even into the smallest acts, should be put our heart, mind and soul. Thank you for reading my article