Free thyroxine, a hormone produced by the hypothalamus, is of great importance in ensuring the normal functioning of the thyroid gland. Most of the fraction of the hormone T4 is not associated with carrier proteins, which is why its name "free thyroxine" is explained.
Blood test for free thyroxine
T4 affects the human body as follows:
- increases oxygen consumption by cells;
- normalizes metabolism in tissues;
- clears vessels of excessive cholesterol;
- stimulates the synthesis of proteins;
- prevents thrombosis;
- ensures normal development and growth;
- supports the process of heat formation.
In addition, the hormone T4 affects the ability of a woman to conceive, endure and give birth to a healthy baby. In connection with the importance of the hormone for the life of the body, it is necessary to know whether the level of free thyroxine is normal. To determine the concentration of free thyroxine in the blood plasma in the laboratory is a venous blood sampling.
Norm of free thyroxine depends on sex and age. In men, the content of the hormone is somewhat higher than that of women. The normal levels of T4 in women are as follows:
- at the age from 14 to 40 years - 100-120 nM / l;
- after 40 years - 80-100 nM / l.
In pregnant women, the concentration of free thyroxin is 120-140 nM / L, and this is due to the fact that part of the maternal hormone goes to the formation of the child's bone system. The dependence of the content in the blood T4 on the time of day and season of the year was established.
The maximum level is marked:
- in October and February;
- from 8-00 to 12-00.
The minimum value is:
- in June-August;
- from 23-00 to 3-00.
Increase of free thyroxine content
Free thyroxine increased at:
- myeloma ;
- kidney damage;
- liver diseases, including those with hepatitis;
- hypertrophic changes in the thyroid gland of Based's disease and Graves' disease;
- violations of metabolic processes;
- excess body weight.
Also, the increase in the level of the hormone T4 can arise as a result of self-medication of cardiovascular ailments, with improper intake of certain medical preparations (Aspirin, Danazol, Levotheoxin, Furosemidonoma, etc.) and uncontrolled use of Heparin in the treatment of thrombosis.
Free thyroxine lowered
The content of free thyroxin below the norm is typical for such conditions and diseases as:
- physical overstrain;
- protein diet for weight loss;
- long-term stressful situations;
- lack of iodine;
- goiter;
- hypothyroidism ;
- benign thyroid tumors;
- inflammation of the pituitary gland;
- craniocerebral trauma;
- lead poisoning.
Sometimes a lowered free thyroxin is noted when taking medications, including:
- excessive use of certain antidepressant drugs;
- an overdose of Clofibrate and other medications that dilute the blood;
- use of oral contraceptives;
- the use of anti-tuberculosis, anti-inflammatory, anticonvulsant drugs, glucocorticoids and drugs for the treatment of diffuse toxic goiter.
Attention! A decrease in T4 can signal that the patient is taking drug-containing substances!
Slight changes in the content of free thyroxine in the blood - not an occasion for anxiety, but a noticeable change in the hormonal status and the subsequent deterioration of the state of health require examination by specialists. So, in order to determine the dynamics of changes in the level of free T4 in thyroid diseases, it is recommended to donate blood 1-3 times a month for two years.