Today, very often for the diagnosis of a variety of diseases, blood tests for hormones produced by the thyroid gland are prescribed. This study is to determine the level of thyroid hormones( thyroxine and triiodothyronine - respectively, T4 and T3), which are produced by the thyroid gland, as well as the associated thyroid-stimulating hormone( TSH), produced by the pituitary gland. The analysis allows the endocrinologist to assess the status of an important organ of the human body as a whole and correctly prescribe the treatment when a deviation from the norm is detected.
Characteristics of hormones
Thyroid hormone is produced in the pituitary gland, which is located at the base of the brain. Its functional purpose is stimulation of thyroid hormone production:
- T3( triiodothyronine),
- T4( thyroxine).
Triiodothyronine and thyroxine are very important highly bioactive substances that are responsible for the overall health of a person. T3 and T4 provide the right metabolism, normal operation of the vegetative and cardiovascular and digestive systems, and also support the mental functions of the human body. Thyroid stimulating hormone, triiodothyronine and thyroxine are interdependent. On the one hand, TSH stimulates the production of Thyroid and T4, and when their level rises, these substances suppress the production of TSH in the pituitary gland. Thus, in a healthy human body self-regulation of the hormonal balance occurs, based on "feedback".
The condition at which the production of T3 and T4 in a normal amount occurs is called euthoriosis. In endocrinology, the following pathologies are distinguished with a violation of the norm:
- Hypothyroidism - with a decrease in the direction of decrease.
- Hyperthyroidism - with a deviation in the direction of increase.
- Thyrotoxicosis - with active production of bio-substances.
Norm TTG
An important indicative analysis is the determination of TSH in the blood. Such a study is prescribed simultaneously with the delivery of tests for T3 and T4, produced by the thyroid gland. Norm TTG varies depending on age and can make in mUd / l:
- for newborns - 0,7-11;
- for children older than 10 weeks - 0,6-10;
- to two years - 0.5-7;
- up to five years - 0,4-6;
- to 14 years - 0,4-5;
- for adults - 0,3-4.
The greatest amount of TSH in healthy people is found in the morning. If the level is much higher than normal, it means that the thyroid gland produces insufficient amounts of thyroid-stimulating hormones and this can indicate such pathologies:
- of the psyche,
- adrenal gland failure,
- absence of the gallbladder,
- hypothyroidism,
- of the pituitary tumor.
In addition, an elevated level of TSH in the blood is observed in pregnant women and with prolonged excessive physical exertion. In such cases, the normalization of the hormonal background occurs after the disappearance of the causes that caused the imbalance. For pregnant women it is normal to raise the level of TSH, especially in the first trimester, when the thyroid gland of the fetus is in the formative stage and does not work properly.
If the level of thyroid-stimulating hormone is low, this primarily indicates a decreased function of the pituitary gland. Among the household causes that are capable of provoking a decrease in TSH should be noted strong psychological stress and overdose of hormone-containing drugs. In addition, a decrease in this biomaterial in the blood can occur with the development of the following pathologies:
- thyrotoxicosis,
- benign formations on the thyroid,
- brain tumors.
Norm of the hormone T4
The analysis for the content of thyroxine in the blood is practically always prescribed simultaneously with the study of the level of TSH.The combination of the two values allows you to assess how much the thyroid gland is coping with its functions. Thyroxine in the blood can be associated with proteins( with albumins) and not bound( free T4).The total value is a common thyroxine, but the amount of free thyroxin is considered more informative.
The regulatory total T4 is measured in nmol / l. In newborns, the highest level of thyroxine is found, which is in the range of 69.6-219.In the age group up to 20 years, the upper limit is gradually reduced. Therefore, the results of analyzes on special tables are deciphered. After 20 years, the regulatory range of the hormone remains unchanged and is:
- for men - 59-135;
- for women -71-142.
In pregnancy, overdose of hormonal drugs, violations in the liver and kidneys, it is important to determine the level of free thyroxine in the blood to exclude the setting of a false diagnosis. The norm of free T4, most often, is measured in pmol / l and is in the following ranges:
- for men - 12,6-21;
- for women is 10,8-22.
For pregnant women, the permissible normative values differ and change in terms of trimesters:
- in pregnancy less than 13 weeks - 12.1-19.6;
- during pregnancy from 13 weeks to 28 weeks - 9.6 -17;
- in pregnancy 28 weeks to 42 weeks - 8.4-15.6.
The most common cause of elevation of thyroxine is Bazedova's disease. Other common pathologies that lead to an increase in the production of bioactive substances by the thyroid gland are liver and kidney diseases, obesity and benign thyroid tumors.
Lowering thyroxine below the norm is most often due to the development of thyroiditis. In addition, a low T4 level is observed with:
- remote thyroid,
- iodine deficiency in the body,
- inadequate amount of proteins in the diet,
- lead poisoning.
Norm T3
The concentration of triiodothyronine in the blood is much lower than that of thyroxin, but its biological activity is higher. T3 influences the oxygen supply of all tissues of the human body, accelerates protein metabolism, lowers cholesterol and participates in the production of vitamin A in the liver. An analysis of the amount of triiodothyronine in the blood is usually prescribed when it becomes necessary to clarify the state of the thyroid gland. TotalT3 is determined by the following normative ranges of values, unit of measurement nmol / l:
- to 20 years - 1.23-3.23;
- to 50 years - 1.08-3.14;
- after 50 years - 0,62-2,79.
More indicative is the level of free triiodothyronine, its rate is 2.6-5.7 pmol / l. With an increase in the amount of free T3, severe headaches and elevated body temperature can be observed for a long time. External signs are hand trembling and emotional imbalance. For a lower level of triiodothyronine is characterized by rapid fatigue, muscle weakness and uncaused convulsions. Also, with a low amount of T3, sleep and brain activity are disturbed, which is manifested by a slowing down of thinking.
Indications for analysis of hormones and the rules of their delivery
If a patient addresses an endocrinologist with complaints about his condition for the first time or for the purpose of preventive examination, the doctor for the evaluation of thyroid functions will necessarily assign the following tests:
- for thyroid stimulating hormone,
- per levelfree thyroxine,
- to the level of free triiodothyronine.
This will be enough to make the right conclusions about the state of the thyroid gland. The general standard for the initial examination is not indicative. If there is a suspicion of serious pathology, then other studies may be prescribed, but this decision in each case the endocrinologist takes individually. Also, the amount of bioactive substances produced by the thyroid gland may interest doctors of other specializations in order to clarify the diagnosis. Indications can be:
- impotence,
- infertility,
- cardiac arrhythmia,
- delay in sexual and mental development,
- amenorrhea,
- decreased libido.
Venous blood for analysis is always given in the morning on an empty stomach. It is important a month before the study to refuse to take hormonal drugs, and three days before taking blood to exclude the use of iodine-containing drugs. On the eve of the study, avoid stressful situations and minimize physical stress.
Assays for thyroid-stimulating hormone( TTG), produced by the pituitary gland, and hormones produced by the thyroid( T3 and T4), allow an accurate diagnosis and correct treatment. Their values depend, first of all, on the age factor, but can change under certain external conditions.
