What are the five items of thyroid function examination for?

Thyroid function test is a very important part of modern medicine, and it is almost a must-check item in the physical examination list, because thyroid function has a great impact on the health of the body. Problems with thyroid function can cause great damage to the body and induce thyroid diseases, etc. Thyroid function can generally be determined using five indicators. Let’s take a look at what the five items of thyroid function examination are for.

The five thyroid function tests refer to five health test data of the thyroid gland, namely the measurement of thyroxine (T4), triiodothyronine (T3), thyroid stimulating hormone (TSH), free T3, and free T4.

The five thyroid function tests have different values, namely T3 reference value 0.92-2.79, T4 reference value 55.5-161.3, FT3 reference value 3.54-6.47, FT4 reference value 11.48-23.22, TSH reference value 0.35-5.5. These are thyroid hormone tests, and they are all within the reference range, indicating that there is no problem with thyroid hormone secretion, and basically ruled out problems such as hyperthyroidism, hypothyroidism, and thyroid tumors.

Clinical significance:

The physiological functions of the thyroid gland are mainly to promote the metabolism of the three major nutrients, regulate growth and development, increase tissue oxygen consumption, promote energy metabolism, increase heat production and improve basal metabolism. When the thyroid gland function is disordered, hyperthyroidism or hypothyroidism will occur.

Among them, thyroxine (T4) and triiodothyronine (T3) are synthesized in the thyroid follicular epithelial cells. Under the stimulation of pituitary thyroid stimulating hormone (TSH), they undergo a series of changes and are released into the blood. More than 99% of T3 and T4 in the blood are bound to plasma proteins, mainly to thyroxine-binding globulin. Only about 0.4% of T3 and 0.04% of T4 in the total plasma are free. Only free T3 and T4 can enter the target cells to exert their effects, and the part bound to the protein regulates and stabilizes the free T3 and T4. The synthesis and secretion of thyroid hormones are mainly regulated by the hypothalamus-pituitary-thyroid axis. The fluctuation of free T3 and T4 levels in the blood negatively feedbacks and causes an increase or decrease in the release of thyrotropin-releasing hormone TRH from the hypothalamus and thyroid-stimulating hormone TSH from the pituitary. The main function of TRH is to promote the synthesis and release of TSH by the pituitary gland. TSH stimulates the proliferation of thyroid cells and the synthesis of thyroglobulin, and promotes each process in the synthesis of thyroid hormone from iodine uptake to release.