Total Thyroxine (T4 total)
Why this test?
- For the function disorders diagnosis of the thyroid gland.
- To control the diseas treatment of the thyroid gland.
- To diagnose the causes of female infertility.
- For the diagnosis of congenital hypothyroidism.
In what cases is it prescribed?
With symptoms of hypo- or hyperthyroidism. Symptoms of hyperthyroidism: rapid heartbeat, increased irritability, weight loss, insomnia, hand tremors, weakness, rapid fatigue, diarrhea (in some cases), increased sensitivity to light, visual impairment, swelling around the eyes, dryness, redness, exophthalmos ( protrusion of the eyeballs). Symptoms of hypothyroidism: weight gain, dry skin, constipation, cold intolerance, swelling, hair loss, irregular menstruation in women. With severe hypothyroidism, complications such as heart rhythm disturbances, ischemia of the heart muscle, and coma may occur. In children, hypothyroidism can cause a delay in physical and mental development - cretinism.
As part of a preventive examination together with other laboratory tests (general analysis of blood and urine, various biochemical indicators).
Periodically when monitoring the treatment of thyroid diseases (together with an analysis of thyroid-stimulating hormone) - at least once every 3 months.
During pregnancy, women who are prone to thyroid diseases or already suffer from them - for timely detection of thyroid hormone secretion disorders, as they can lead to termination of pregnancy or congenital pathology in the fetus.
In the first days of life, babies born to mothers with thyroid diseases.
In the course of the study, it is possible to determine the concentration in the blood of the protein-bound and non-protein-bound fractions of the main thyroid hormone - thyroxine. This is one of the most important tests for evaluating the function of the thyroid gland, however, its results depend on the number of thyroxine-binding proteins in the blood plasma, which does not allow determining the concentration of the biologically active fraction of the hormone. The main proteins that bind thyroxine in blood plasma are albumins. The ratio of the free and bound fraction of thyroxine and the activity of the hormone depend on their number. Thyroxine makes up about 90% of the total amount of hormones secreted by the thyroid gland.
Most often, this analysis is prescribed together with the study of the concentration of thyroid-stimulating hormone - the regulator of the function of the thyroid gland and the free fraction of thyroxine.
The thyroid gland controls metabolism and the intensity of energy consumption by the body. It works according to the feedback mechanism with the pituitary gland. The pituitary gland secretes thyrotropin (TSH) in response to a decrease in thyroxine concentration, thereby stimulating the thyroid gland to produce hormones. When the level of thyroxine increases, the pituitary gland begins to produce less thyroid-stimulating hormone and the secretion of thyroxine by the thyroid gland decreases.
If the thyroid gland is unable to produce a sufficient amount of thyroxine or thyroid-stimulating hormone is not produced enough to stimulate it, symptoms of hypothyroidism appear. In such patients, body weight increases, the skin dries up, fatigue increases, they become very sensitive to cold, and in women the menstrual cycle is disturbed. When the thyroid gland secretes increased amounts of thyroxine, the metabolic processes in the body and the production of energy in the cells increase, which leads to hyperthyroidism. Rapid heartbeat, anxiety, weight loss, sleep disturbances, tremors in the hands, dry and red eyes, facial swelling are the main symptoms of this disease.
The most common cause of thyroid hormone imbalance is autoimmune damage to the gland. The most common of them are Based's disease (causes hyperthyroidism) and Hashimoto's thyroiditis (hypothyroidism). Complications of hyper- and hypothyroidism are cancer of the thyroid gland, thyroiditis. The effect of these diseases on the function of the thyroid gland can be determined by analyzing thyroxine.