Normal levels of thyroid hormones T3, T4

The article was professionally consulted with General Internal Medicine Doctor - Department of Examination & Internal Medicine - Vinmec Nha Trang International General Hospital.

Thyroid function is influenced not only by the thyroid gland but also by the pituitary gland (a gland that produces thyroid-stimulating hormone called TSH). When diagnosing thyroid pathology is indicated to perform a total of many types of combined tests.

The thyroid gland secretes two main hormones, thyroxine (T4) and triiodothyronine (T3). The amount of T4 and T3 hormones secreted by the thyroid gland is regulated by the thyroid-stimulating hormone (TSH) of the pituitary gland. When you want to determine thyroid disease, it is necessary to simultaneously conduct thyroid function tests including: TSH , fT4, fT3.
The purpose of conducting thyroid hormone tests, along with related tests, is to diagnose whether the thyroid gland is functioning as it should, and this test is also very important in the diagnosis of thyroid disorders. thyroid disease and the root cause of such disorders to give timely advice and treatment.

TSH is a pituitary hormone that sends signals to the thyroid gland. When the pituitary gland detects that there is less thyroid hormone in the blood, it will produce more TSH to stimulate the process to stimulate the thyroid gland to produce more thyroid hormone. Conversely, if the pituitary gland detects that there is too much thyroid hormone, it will reduce the production of TSH and the thyroid gland will also decrease the production of thyroid hormone.
The TSH test may be used in conjunction with the FT4 test or sometimes the FT3 test to diagnose dysfunctional thyroid disease and to monitor thyroid replacement therapy in patients with hypothyroidism, or as Monitor treatment in patients with hyperthyroidism and sometimes conduct tests to evaluate pituitary function. Triiodothyronine (T3) is a hormonal hormone whose function is primarily responsible for the development of thyroid hormone effects on various target organs. T3 hormone is mainly produced outside the thyroid gland, especially in the liver, by enzyme deiodination at the 5' position of T4. Therefore, serum T3 hormone levels will reflect the functional status of peripheral tissues rather than the ability to secrete thyroid gland. Thyroid hormone thyroxine (T4) is a physiological component of the thyroid regulatory loop and has an impact on the body's general metabolism. Free thyroxine (fT4) is biologically active. Quantitative testing of free thyroxine is important in routine clinical diagnosis and is also appropriate for monitoring thyroid suppression therapy.
Normal biological value: A TSH reading is normal if the result is in the range of 0.4 to 5 mIU/L (milli-international units per liter).
Normal T3 T4 index (for adults) when T3 hormone reaches 1.3 - 3.1 nmol/l or 0.8-2.0 ng/ml. The values ​​of T3 will increase and decrease in proportion to T4, however, in some cases (thyrotoxicosis caused by T3), T3 increases but T4 is normal.

The FT4 index is normal (for adults) when it reaches 12-22 pmol/l (0.93-1.7 ng/dL). If the patient is not taking any thyroid medication, this test is a measure of thyroid function. Certain medications can alter T4 results such as: epilepsy drugs, heart medications, or aspirin...
When a person has hypothyroidism and underactive thyroid, the TSH will become high even though even though T3 and T4 levels are normal. TSH will increase when circulating thyroid hormone is low, which is a sign of impaired pituitary function. In short, the thyroid gland is one of the very important organs, playing a role in releasing hormones for the body's cycle of operation. Although it is very small in size, the thyroid gland is an important organ and is easily invaded by bacteria and viruses, causing inflammation, affecting the patient's health.
In fact, thyroid diseases are often overlooked and not diagnosed early, accounting for about 20-60% of the total number of people with the disease. This has made the examination and treatment less effective, even when detected, the disease has entered a more severe stage and faced dangerous complications. Therefore, each person should learn about thyroid disease for themselves to have effective prevention measures and safe disease screening.