Analysis For Thyroid Hormones (norms Of Hormones TSH And T4)

2024 Author: Josephine Shorter | [email protected]. Last modified: 2024-01-17 02:10

Analysis for thyroid hormones (norms of hormones TSH and T4)

Content:

• What thyroid hormones are tested?
• Why does the thyroid gland produce hormones?
• What tests are passed in different cases?
• Norms of thyroid hormones in women
• How to recognize thyroid disease by analysis?
• Thyroid hormone tables
• How to get tested for thyroid hormones correctly?
• Deciphering hormone test results
• Features of the analysis for T4 during pregnancy

What thyroid hormones are tested?

At the moment, the Internet is replete with materials on medical topics. In particular, there are articles on the topic of blood tests to assess the level of production of thyroid hormones. As a rule, these texts were not written by doctors, and therefore are illiterate and contain a lot of factual errors. Such materials will not answer the questions, but will only confuse the reader even more.

In addition to triiodothyronine (T3) and thyroxine (T4), unknowing authors include TSH and TPO in the number of thyroid hormones. But this is fundamentally wrong.

The first two hormones are categorized as thyroid hormones quite rightly. They are actually synthesized by the thyroid gland. While TSH is a nonspecific hormone, the synthesis of which is carried out by another endocrine organ - the pituitary gland.

The pituitary gland is a small gland located in the brain. The main function of the pituitary gland is to regulate the work of the entire endocrine system by releasing active substances (it must be said that it secretes a number of active substances, their number is determined by dozens).

Thus, TSH (the so-called thyroid-stimulating hormone) is the "signaling" hormone of the pituitary gland. Thanks to its effect, the thyroid gland increases the intensity of work and releases more active substances.

TPO also cannot be attributed to thyroid hormones. This substance is not a hormone at all, but an antibody. The immune system releases it to destroy iodine-containing substances. However, all four of the above substances must be considered together, since they are closely related to each other and form the mechanism of the thyroid gland.

Thyroxine (tetraiodothyroninyl T4). One of the two main thyroid hormones. It makes up the majority of all compounds synthesized by the thyroid gland (up to 90%).

Triiodothyronine (T3). It is another thyroid hormone. Its activity exceeds that of T4 by 1000%. T3 contains three iodine atoms, not 4, so the chemical activity of the hormone increases significantly. Many people consider triiodothyronine to be the main thyroid hormone, and T4 is the "raw material" for its production. T3 is synthesized from T4 by acting on the 4-atomic hormone with selenium-containing enzymes.

Both TK and T4 are specific thyroid hormones, that is, they are classified as thyroid hormones. Their synthesis is necessary for the normal functioning of the autonomic and nervous systems, as well as for the basic metabolism, due to which the functioning of autonomous energy-consuming processes occurs: contraction of the heart muscle, conduction of nerve signals, etc.

Specific hormones can exist in either a free or bound state. For this reason, several columns are often highlighted in the results of laboratory tests: free T3 hormone or free T4 hormone. It can also be referred to as FT3 (Free T3) or FT4 (Free T4). Most of the thyroid substances are in a state associated with protein compounds. When hormones are released into the blood, they combine with a special protein TSH (thyroid-binding globulin) and are transported to the necessary organs and systems. Once the transport is complete, the thyroid hormones are released again.

A free hormone has activity, therefore, to assess the functioning of the thyroid gland, the study of this indicator is necessary and the most informative.

TSH is a pituitary hormone that affects the functioning of the thyroid gland by acting on the receptors of thyrocyte cells.

Such exposure can cause the following consequences:

• Increasing the intensity of the synthesis of thyroid hormones (due to the fact that the cells of the thyroid gland begin to work more actively);
• Extension of thyroid tissue. As tissues grow, diffuse changes in the organ intensify.

Antibodies

The next most important indicator is antibodies. Assessment of the amount of antibodies to iodine-containing compounds is necessary for a correct diagnosis.

There are three types of antibodies:

• Proteins for TPO (thyroperoxidase);
• Proteins for TG (thyroglobulin);
• Proteins for rTTG (TSH receptor).

In the results of laboratory tests, abbreviated forms of the names of substances are most often indicated. AT - antibody. TG, RTTG, TPO.

Antibodies to thyroperoxidase

TPO is one of the main enzymes directly involved in the synthesis of thyroid hormones. Depending on the degree of deviation of the result from the normal one, an increased concentration of these antibodies may not appear in any way, or lead to hypothyroidism (a decrease in the level of thyroid hormone production). The rise in levels is relatively common: about 10% of women and half the number of men (5%) globally.

Since the concentration of iodine-containing substances in the thyroid gland is maximum, thyroperoxidase disrupts the work of thyrocyte cells. As a result, the amount of thyroid hormones produced decreases. It is impossible to unequivocally call the excess of the indicator a marker of the disease, however, studies and statistics show that an increase in TPO content leads to hypothyroid diseases of the thyroid gland about 5 times more often than in similar cases when the level of hormones is normal.

A blood test for the presence of this substance is carried out in order to detect diffuse toxic goiter of the thyroid gland and autoimmune diseases.

Antibodies to thyroglobulin

An excess of the level of antibodies to thyroglobulin is much less common than a similar result for antibodies to thyroperoxidase. According to statistics, the number of persons with a detected deviation from the norm in a larger direction is about 5% of women and about 3% of men.

The indicator is quite variable and may indicate the presence of two types of diseases:

• DTZ of the thyroid gland or Hashimoto's autoimmune thyroiditis;
• Cancer of the thyroid gland.

In the second case, they talk about two forms of cancer: follicular or papillary, since it is with these types of tumors that an increased production of TG occurs. Thyroglobulin is produced only by thyroid cells or malignant tumor cells. If an excess of the norm is detected, both the patient and the attending physician should be alert. TG simultaneously acts as a tumor marker.

After the operation to remove the tumor along with the affected thyroid gland, the thyroglobulin level should drop to minimum levels (down to zero). If this does not happen, the reason lies in the recurrence of cancer.

It should be borne in mind that with an increased level of antibodies to TG, the result may be incorrect. Antibodies create a single structure with the iodine-containing TG protein and are so tightly bound that it is impossible to distinguish between the protein secreted by lymphocytes and thyroglobulin itself in a laboratory study. To assess the level of TG, it is necessary to conduct an independent analysis.

It should also be borne in mind that an excess of the thyroglobulin level is not always an indicator of oncology. It is simply pointless to carry out an analysis for the concentration of TG in the blood in patients with not removed thyroid gland. An excess of TG can be considered a tumor marker only if the gland has been removed.

In patients with other changes in the organ, the TG index may differ from the norm for many reasons: diffuse pathological transformations of the endocrine organ, in which the volume of organ tissue grows, nodular formations, etc. If a relatively healthy patient is assigned a blood test for thyroglobulin, this means only one thing: the clinic conducting the analysis wants to cash in on the person's ignorance and includes in the list of laboratory tests what is not needed.

To detect the presence of cancer in patients whose thyroid gland has not been removed, it is advisable to prescribe a blood test for calcitonin content. This is a really important marker of oncology. It allows you to identify the medullary form of thyroid cancer. C-cell cancer is an extremely dangerous and practically incurable disease in the last stages. Neither chemotherapy nor radiation therapy gives any adequate results. The only way to heal this thyroid tumor is to have surgery on time. For this, it is necessary to timely identify the disease.

As a rule, in patients with diffuse organ changes, the likelihood of developing medullary cancer is minimal. If nodular and diffuse nodular changes in the thyroid gland are present, the appointment of a blood test for calcitonin is mandatory. The study of venous blood should be carried out in conjunction with a fine-needle biopsy.

Antibodies to RTTG

An analysis for the presence of antibodies to thyroid-stimulating hormone receptors is prescribed for patients with confirmed diseases of the thyroid gland (for example, with diffuse-toxic goiter of the thyroid gland).

The study of venous blood is carried out against the background of conservative therapy with drugs that reduce the level of production of specific active substances. Studies show that the outcome of the disease often depends on the level of decrease in antibodies to rTTG. If therapy does not bring the desired effect, and the degree of antibody concentration does not decrease, this means an unfavorable course of the disease. In this case, the patient should be prescribed surgical treatment.

However, the excess of the indicator in itself is not an absolute indication for surgical intervention. When making a decision, the doctor must proceed from a system of factors: the general course of the disease, the degree of nodular and diffuse changes, the size of the goiter, etc.

Thus, a person with suspicion of thyroid pathology or with a confirmed organ disease should conduct a venous blood test for the following indicators:

• T3 (triiodothyronine);
• T4 (tetraiodothyronine or thyroxine);
• TSH;
• Antibodies to thyroglobulin;
• Antibodies to thyroperoxidase.

To investigate other indicators or not - the endocrinologist decides, based on the patient's history.

Why does the thyroid gland produce hormones?

The thyroid gland produces hormones to create the foundation necessary for the normal functioning of all systems and organs. Thanks to it, a stable energy metabolism in the body and the work of the autonomic nervous system are ensured.

Figuratively, an organism can be imagined as a multi-storey building powered by coal, and the functioning of the thyroid gland is like the operation of a coal-fired boiler plant. Charcoal in this case is the thyroid hormones themselves.

If too much coal is added to the boiler room, it becomes hot in all rooms. People who work in the building suffer from too high temperatures, sweat, pass out, etc. If you add too little coal, the heating effect will not be enough, the rooms will freeze. People will begin to suffer from the cold, dress warmer and try to hide from the low temperature.

Obviously, in both cases, there is no normal mode of operation, and everyone will only think about how to hide from adverse conditions.

In this example, human workers represent all other hormones (pituitary gland, adrenal glands, pancreas, etc.) produced by the human body, as well as organs and systems.

In a normal state, the role of the thyroid gland is practically invisible, but as soon as failures and violations begin, serious consequences arise. The thyroid gland provides the necessary base for minimally effective and stable functioning of the whole organism.

Depending on the type and form of pathological changes in the thyroid gland, two main cases are possible:

• Too many hormones are synthesized (excess);
• Specific hormones are not enough for the normal functioning of the body (deficiency).

Excess thyroid hormones (thyroid hormones)

By analyzing venous blood, it is quite easy to determine the excess amount of thyroid hormones. This situation is called "hyperthyroidism", and its consequences for the body are called thyrotoxicosis.

With an excess of thyroid hormones, a number of symptoms are observed:

• Hyperthermia. In other words, an increase in body temperature. Persistent and periodic, up to subfebrile condition (marks at 37.1 - 37.7);
• Strengthening mental and physical activity. The person becomes aggressive, nervous and overly excitable;
• Change in body weight. Body weight is steadily falling, despite the fact that the patient has a brutal appetite and consumes more food;
• Tremor. Trembling of the limbs is noted (fingers and hands themselves shake), and sometimes the head.

At later stages or with a significant deviation of the level of thyroid hormones from the norm, more formidable manifestations of hyperthyroidism are observed:

• Cardiac dysfunction. Hypertonicity of blood vessels, increased pressure and persistent tachycardia even in the absence of physical activity;
• Disorders of the nervous system. A person suffers from intelligence, concentration and memory;
• Disorders of the digestive tract. Frequent constipation or diarrhea, "indigestion", indigestion and intestinal upset occur.

With hyperthyroidism, systemic disturbances in the work of all organs are noted.

Elevated levels of triiodothyronine and tetraiodothyroxine (T3 and T4) are an indicator of hyperthyroidism. In this case, the level of the pituitary hormone TSH decreases sharply. If an increased concentration of free thyroid hormones is detected in the blood, even to an insignificant extent, the patient is prescribed special treatment in order to normalize their content.

If the excess is significant, and conservative treatment does not give the necessary results, an operation is prescribed.

Lack of thyroid hormones

A condition in which the level of specific thyroid substances in the blood is below a specified minimum is called hypothyroidism.

Hypothyroidism is characterized by the following manifestations:

• Hypothermia. Decrease in body temperature to 35.5 ° C. The temperature does not return to normal even with physical activity;
• Reduced pressure. Blood pressure drops below normal levels (up to 90-85 / 60-50). Hypotension is observed;
• Swelling. Fluid is excreted from the body at a very low rate. The normal functioning of the excretory system is disrupted, the kidneys cope worse. Serious swelling of the limbs and face occurs;
• Insomnia. At night the patient cannot sleep, and in the daytime he feels weak, lethargic and weak. The biological rhythm gets lost;
• Increase in body weight. Obesity is often associated with hypothyroidism. The reason for this is a decrease in the metabolic rate;
• Insufficient efficiency of the work of other endocrine glands. Contributes to the occurrence of adverse effects. A decrease in the level of production and exposure of sex hormones entails the extinction of libido and sexual dysfunctions, disruptions of the monthly cycle. The weakening of the secretion of digestive hormones contributes to unstable blood sugar levels, malfunctions of the digestive system. A decrease in the production of pituitary substances affects the functioning of the nervous system and the body as a whole;
• Deterioration of the condition of the skin and nails. The skin becomes dry and flabby, nails - brittle, hair falls out.

With a decrease in the level of hormones to critical levels, there is also a deterioration in the work of the heart (bradycardia, etc.). The analysis of venous blood reveals a reduced level of thyroid substances. Simultaneously with the analysis for hormones, an analysis for antibodies to thyroid peroxidase (TPO) should also be carried out in order to identify the cause of the dysfunction. The source may be an autoimmune disease.

At the same time, both too large and insufficient number of thyroid hormones negate the reproductive function of the human body. Problems with the thyroid gland are one of the main causes of difficulties with pregnancy. Women, both already pregnant and planning motherhood, also need to pay attention to the TSH indicator.

Hormonal dysfunction in children and adolescents is a serious problem. If there is an excess or deficiency of thyroid hormones at an early and transitional age, there is a risk of mental retardation due to underdevelopment of the brain or problems with the nervous system.

Thus, the active substances of the thyroid gland, with all their invisibility, play a major role in the functioning of the body and the normal life of a person. A deviation in the level of thyroid-stimulating active substances leads to severe systemic disorders that significantly reduce the quality of life.

What tests for thyroid hormones are taken in different cases?

if the endocrinologist recommended passing hormonal tests, but did not specify which indicators are required, it is important to find out exactly. With a clear understanding, the result will be as informative as possible, and you will not have to pay extra money for unnecessary analyzes.

Initial examination of the patient

If the patient comes to the endocrinologist for the first time with complaints or for the sake of a preventive examination, it is necessary to investigate the following indicators:

• TSH (thyroid stimulating hormone);
• T4 St. (free tetraiodothyroxine);
• T3 St. (free triiodothyronine);
• AT to thyroperoxidase (TPO).

This list will be enough to assess the general condition of the thyroid gland.

Suspected elevated hormone levels

If the patient has signs characteristic of an excess of thyroid hormones (hyperthermia, etc.), hyperthyroidism (thyrotoxicosis) must be excluded.

In this case, the list of indicators for analysis will look like this:

• TSH (thyroid stimulating hormone);
• T4 St. (free tetraiodothyroxine);
• T3 St. (free triiodothyronine);
• AT to thyroperoxidase (TPO);
• AT to TSH receptors (rTTG).

The latter indicator may most clearly indicate the presence of hyperfunction of the thyroid gland.

To monitor the effectiveness of treatment with thyroid drugs, the following are investigated:

• T4 free;
• TSH.

Analysis of other indicators is not required, since the figures remain the same during specific treatment or their dynamics is not of interest.

In the presence of nodular changes in the thyroid gland

If nodules are present in the thyroid gland, the primary blood test should include the determination of the level of the following substances:

• TSH (thyroid stimulating hormone);
• T4 St. (free tetraiodothyroxine);
• T3 St. (free triiodothyronine);
• AT to thyroperoxidase (TPO);
• Calcitonin (tumor marker).

The latter indicator allows you to accurately determine the oncological diseases characteristic of the nodular goiter in the early stages.

During pregnancy

During pregnancy, the following are examined:

• TSH (thyroid stimulating hormone);
• T4 St. (free tetraiodothyroxine);
• T3 St. (free triiodothyronine);
• AT to thyroperoxidase (TPO).

It is important to keep in mind that in pregnant women, the level of TSH hormone is often below the indicated standard. This does not indicate the presence of diseases or pathological processes.

If an operation was performed to eliminate a papillary or follicular tumor of the thyroid gland

It is necessary to make sure that the hormonal level and the level of specific proteins are normalized in order to exclude the recurrence of cancer.

Investigated:

• TSH (thyroid stimulating hormone);
• T4 St. (free tetraiodothyroxine);
• AT to thyroglobulin;
• Protein thyroglobulin.

If surgery was performed to resect a medullary tumor

After such an operation, the following are examined:

• TSH (thyroid stimulating hormone);
• T4 St. (free tetraiodothyroxine);
• Tumor marker calcitonin;
• CEA specific cancer antigen.

Advice

When deciding whether to take tests for the concentration of thyroid hormones in the blood, you need to follow a small list of rules. They will increase information content and avoid unnecessary cash spending:

• The concentration of antibodies to thyroperoxidase is tested once. Repeated blood donation to determine this indicator will not bring any information, since changes in the numerical value do not in any way affect the dynamics of the course of the disease. A competent endocrinologist with this sign does not recommend taking such an analysis twice;
• Free and bound thyroid hormones cannot be tested in the same assay. The result for both those and other indicators will be blurred. If such a comprehensive analysis is strongly recommended to you, it is simply cheating in order to increase your revenue;
• Patients with a non-operated thyroid cancer should not be tested for thyroglobulin. This protein is investigated only after removal of the thyroid gland and is a tumor marker of recurrence. Even in a relatively healthy person, the level of this protein can exceed the norm. This does not mean anything. If a doctor or laboratory insists on including thyroglobulin in the analysis, it is a fraudulent maneuver to extract money;
• If the patient does not have a suspicion of hyperthyroidism, it is not worth examining AT to a thyroid-stimulating substance. This analysis costs a lot of money and must be submitted strictly according to the indications of a competent specialist in order to exclude thyrotoxicosis or to assess the dynamics of the therapy being performed with confirmed thyroid hyperfunction;
• Calcitonin is tested once. If no new nodes have appeared in the patient since the last check of the level of calcitonin in the blood, it is pointless to take this test. The same applies to the operation performed to remove the oncological neoplasm. Only these two cases are grounds for re-passing the test for calcitonin in order to exclude the appearance of tumors and relapse.

Norms of thyroid hormones in women

It should be noted that uniform hormone norms are a thing of the past long ago. Now the norm is determined depending on the type of apparatus on which the blood is examined, and the type of reagents used. The "benchmark" indicators are the figures recorded in international documents and agreements. Therefore, you can still talk about approximate numbers.

The norms of specific thyroid hormones and the pituitary hormone TSH are universal for both women and men. They are characterized by the same numbers.

Triiodothyronine (T3 hormone) in a free state

The study of this substance is associated with a number of technological difficulties and requires increased skill and attention from the personnel. If the technology is violated, the indicator may be unreasonably overestimated. If there are doubts about the correctness of the result, the patient is assigned an analysis of the bound hormone (total T3).

The norm in modern clinics and laboratories is from 2.6 to 5.7 petamol / liter. Errors in T3 research are very common.

As a general rule, the analysis is submitted once. Research is required again in a number of cases:

• If the level of triiodothyronine is higher than the norm, and the thyroid-stimulating hormone is within the normal range;
• If the level of triiodothyronine is below normal, and thyroid-stimulating hormone is within normal limits;
• If the level of triiodothyronine is below normal, and tetraiodothyronine is within the normal range.

Free tetraiodothyronine (T4 hormone)

When analyzed in modern laboratories, its norm is in the range of 9.0-19.0 petamol / liter. In different institutions, slight changes in the upper limit are possible within the range of up to 3.0 units, but no more.

There are also a lot of errors in this analysis. If in the description of the laboratory study there is simultaneously a low level of tetraiodothyroxine, and thyroid-stimulating hormone is normal, or vice versa, then the analysis is most likely carried out with violations. This means that the result is inaccurate. In this case, it is recommended to undergo the study again at another institution.

Thyroid stimulating hormone (TSH) rate

Has a standardized value on a global scale. Comprises 0.39 to 3.99 micro-international units per milliliter. If devices of the latest generation are used, the upper limit is increased by 1 unit.

When using the outdated ELISA method, the range in the description will be significantly lower (from 0.26 to 3.45). A high, up to half a unit, error is allowed, therefore it is better to retake the analysis in a modern clinic, moreover, at the same price.

Calcitonin test

The norm for this substance has not been strictly established. Each institution has its own. When carrying out the analysis, great accuracy is required, since even an insignificant, within half a unit, value can indicate the initial and even advanced stage of the formation of a malignant tumor.

It is most reasonable to contact special endocrinological centers for a stimulated analysis. With it, a solution of calcium salt is injected intravenously, and after this, after a certain time interval, the value of the concentration of calcitonin in the blood is estimated.

Thyroid peroxidase antibody test

The rigid norms are not established by international agreements or documents. The upper and lower limits vary from clinic to clinic. The range will be defined on the study description sheet, the form of which is accepted by the laboratory. It is from him that one should build on when assessing the norm.

The most common standards are from 0 to 19-20 units or up to 120. Such a spread is due to the difference in apparatuses and approaches to research.

In a general initial interpretation (by the patient himself), several features should be kept in mind:

• The degree of excess of the concentration of antibodies in the venous blood does not play a role. To assess the state of the endocrine system, the very fact that the indicator goes beyond the upper bar is important. You should not pay special attention and panic, even if the result is exceeded a thousand times;
• A result that is within the laboratory's established range is always accepted as normal. Different indicators, whether they are near the lower or upper border, are absolutely equal. Even if the described result is only one less than the upper bar, this means that the indicator is normal. It is necessary to take this fact into account and not be intimidated by a significant concentration if it fits into the normal range of numbers.

The degree of concentration of antibodies to thyroglobulin

In laboratories equipped with the latest generation equipment, this indicator varies in the range from zero to 4.1 or 65 units.

There can be two reasons for the excess of the antibodies to TG:

• The presence of a rare autoimmune disease (Hashimoto's autoimmune thyroiditis);
• The presence of cancer of the thyroid gland (papillary or follicular cancer).

And in fact, and in another case, to confirm the diagnosis, you need to conduct a set of other studies. So, to confirm Hashimoto's thyroiditis, it is necessary to assess the concentration of thyroid hormones and conduct functional studies. The diagnosis of thyroid cancer requires a fine needle biopsy of the neoplasm.

Even patients with oncology do not always exceed this indicator. Their number is no more than 30%. In other cancer patients, antibodies to thyroglobulin are normal. The reason for this is still not fully understood.

You should also not compare the results obtained by patients in different laboratories. They are not equivalent to each other and cannot be recalculated by the method of proportions, since there is a fundamental difference in technology and approach to research. It is especially important to know this for people who have undergone surgery to remove a malignant thyroid tumor.

Repeated blood donation for such patients helps to identify a relapse of the disease. Therefore, it is advisable to observe one rule: the analysis for the concentration of antibodies to TG is best done in the same laboratory where it was performed the previous time.

How can thyroid disease be recognized by a blood test for hormones?

Disease	TSH	T3 common and free	T4 common and free	Thyroglobulin	Thyroxine-binding globulin	AT to thyroglobulin and AT to thyroperoxidase
Diffuse toxic goiter: subclinical (no symptoms)	low	norm	norm	Rising	Are rising	Are rising
Diffuse toxic goiter: complicated	low	norm	tall	Promoted	Promoted	Are rising
Diffuse toxic goiter: rare	low	tall	norm	Rising	Are rising	Are rising
Hyperplasia of the thyroid gland (adenoma of the glandular tissue)	Reduced	Are rising		Promoted	Promoted	Do not change
Thyroid hypoplasia (endemic goiter)	Increased or normal	Increased or normal	Sharply reduced	Promoted	Promoted	Are rising
Hypothyroidism	Promoted	Concentration decreases		Promoted	Reduced	Are rising
Autoimmune thyroiditis	Increased	In the early stages, T3 and T4 are increased, with the depletion of the thyroid gland, these indicators sharply decrease		Promoted	Promoted	Increased (additionally determined by AT to the TSH receptor)
Thyroid cancer	Increased	Reduced or the norm	Reduced or the norm	Promoted	Reduced	Do not change

Thyroid hormone tables

T3 hormone (triiodothyronine) total

Patient age	Nmol / L	ng / dl
15-20 years old	1.23 to 3.23	80 - 210
20-50 years old	1.08 to 3.14	70 - 205
Over 50 years	0.62 to 2.79	40 - 181

TK hormone (triiodothyronine) free

Patient age	pmol / l	pg / ml * 1.536 = pmol / l
30-50 years old	2.6 to 5.7	1.7 - 3.7

T4 hormone (tetraiodothyroxine) total

Patient age	nmol / l	μg / dl
Men	59 - 135	4.6 - 10.5
Women	71 - 142	5.5 - 11
Pregnant	75 - 230	5.8 - 17.9
Children: 1-5 years old	90 - 194	7 - 15
Children: 5-10 years old	83 - 172	6.5 - 13.4

T4 hormone (tetraiodothyroxine) free

Patient age	pmol / l	ng / dl
Adults	9.0 - 22.0	0.7 - 1.71
Pregnant	7.6 - 18.6	0.6 - 1.45
Children: 5-10 years old	10.7 - 22.2	0.83 - 1.73
Children: 10-15 years old	12.1 - 26.9	0.94 - 2.09

Hormone TSH (thyroid stimulating hormone)

μIU / ml
Men	0.4 - 4.9
Women	0.4 - 4.2
Pregnant women 1 trimester	0.1 - 0.4
Pregnant women 2 trimester	0.3 - 2.8
Pregnant women 3 trimester	0.4 - 3.5
Newborn	0.7 - 11
Children under 2 years old	0.5 - 7.0
Children from 3 months to 5 years	0.4 - 6.0
Children from 5 to 14 years old	0.4 - 5.0

Interpretation of TSH level:

• Less than 0.1 μIU / ml - thyrotoxicosis (suppressed TSH)
• 0.1 to 0.4 μIU / ml - probable thyrotoxicosis (decreased TSH)
• 2.5 to 4 μIU / ml - high-normal TSH level
• 0.4 to 2.5 μIU / ml - low-normal TSH level
• 4.0 to 10.0 μIU / ml - subclinical hypothyroidism
• Over 10.0 μIU / ml - manifest hypothyroidism

Other hormones

Hormone name	Designation	Normal indicator value
TG (thyroglobulin)	TG	<54 ng / ml
Antibodies to thyroglobulin	AT to TG	0-17 U / ml
Antibodies to thyroperoxidase	AT to TPO	<5.5 U / ml
Antibodies to TSH receptors	AT-rTTG:
	AT-rTTG: negative	≤ 0.9 U / l
	AT-rTTG: dubious	1.0 - 1.4 U / l
	AT-rTTG: positive	> 1.4 U / l
Antibodies to MAG (microsomal fraction of thyrocytes)	AT to MAG	<1:99

* LABORATORIES USING DIFFERENT RESEARCH METHODS MAY VARIATE THE INDICATORS

How to take a blood test for thyroid hormones correctly?

Often patients who have to donate blood for thyroid hormones seek help on the Internet. There they expect to find general recommendations on how to prepare for the study, and how the sampling procedure itself takes place.

However, the network is replete with material of extremely dubious content. Even with a cursory examination, a knowledgeable doctor will determine the inconsistency of most of the recommendations. The widespread circulation of such "articles" is aggravated by the fact that sites copy materials from each other, only slightly altering the words, but leaving the essence.

Such recommendations should be avoided. Only in this case the analysis will turn out to be highly informative.

For example, there is often a recommendation to stop taking thyroid medications a month before the test, and iodine-containing medications a week before the test. Such information is fundamentally wrong, but an ignorant person will take it at face value.

In fact, the patient needs to know and follow a number of simple rules:

• The level of all thyroid and related hormones does not depend in any way on the diet. The analysis can be taken both before and after meals. The concentration of these substances in the blood is stable;
• Hormone tests can be done at any time of the day. Although the concentration of thyroid-stimulating hormone varies depending on the time of day, the fluctuations in the indicator are so small that the morning and evening difference does not play a significant role;
• Withdrawing hormonal medications can pose health risks and reduce the effectiveness of treatment. In many cases, it is against the background of conservative therapy that an analysis is carried out, the purpose of which is to determine the effectiveness of treatment and track the dynamics of the process. The only recommendation is not to take medication on the day of the study;
• Iodine-containing preparations do not require withdrawal at all. Taking them cannot affect the concentration of hormones, because the basis of any iodine-containing drug is the salt of this element. The thyroid gland is engaged in the transformation of the original substance, which will not begin to work more actively or worse from taking iodine;
• During the menstrual cycle, the background of sex hormones changes, and not specific substances of the thyroid gland or pituitary hormones. No specific day of the cycle, including the period of menstruation, is not inappropriate for taking a blood test for the level of thyroid hormones, and does not require any special correction of the results.

Deciphering the results of tests for thyroid hormones

Deciphering the indicators obtained in the laboratory without the help of a specialist is a pointless and thankless task. Only a doctor can correctly and correctly interpret the research results. Independent actions in this direction lead patients to the wrong conclusions.

In general, we can talk about some of the most common formulations and typical results. The parameters of the pituitary hormone TSH and specific thyroid-stimulating hormones must be interpreted systemically.

If the hormone TSH is above normal

This almost always means hypothyroidism (decreased thyroid function). As soon as the gland stops producing the level of active substances necessary for the normal functioning of the body, the pituitary gland secretes the stimulating TSH hormone.

If, against the background of an increase in the pituitary hormone, tetraiodothyronine (T4) is below normal, we can talk about obvious hypothyroidism.

There may be a situation in which T4 remains normal, then we are talking about a latent form of hypothyroidism.

In both cases, the thyroid gland is working to the limit. However, if at the same time T4 is normal, the thyroid gland is in euthyroid status, which can develop into more formidable diseases.

With an increase in the level of TSH in a patient, the following clinical manifestations are observed:

• Decreased psychomotor activity. The person looks lethargic and inhibited;
• Sleep problems (you constantly want to sleep, no matter how long a person rests);
• Fragility of bones, nails and hair;
• Weakening of muscle tone.

With euthyroid status, specialized therapy is not prescribed. All assistance to the patient is reduced to constant monitoring of the development of the process. If it stops, no further action is required. If the level of T4 synthesis is below normal, substitution treatment with synthetic thyroid hormones is prescribed until the condition normalizes (from 7 months to a year).

Such a picture of an erroneous analysis result is observed most often in people with existing or just preparing problems with the thyroid gland:

• If TSH is within the established normal values, and tetraiodothyronine is below the norm. There is almost 100% chance of a research error. In 1% of cases, we can talk about Hashimoto's autoimmune thyroiditis or about exceeding the dosage of drugs for the treatment of diffuse toxic goiter;
• If TSH is within the permissible value, and triiodothyronine (T3) is below normal, it is a laboratory error;
• TSH is normal, T4 is also within the acceptable value, and triiodothyronine is below the established level - laboratory error;
• TSH is within the normal range, and thyroid hormones above it is a laboratory error. This is simply impossible, since there are no objective reasons for the intensification of synthesis (there is no signal from the pituitary gland).

Otherwise, if the thyroid-stimulating hormone is above the established norm, a situation of hyperthyroidism (thyrotoxicosis) takes place. If the TSH deviates from the norm, and the thyroxine is higher, we are talking about obvious hyperthyroidism. If specific hormones are within the limits of acceptable values, this is latent hyperthyroidism. In all these cases, immediate medical attention is required.

The only exception is pregnant women. During pregnancy, the level of thyroid-stimulating hormone may fall below the established mark. This is part of a natural physiological process that does not require close attention and treatment.

What is the difference between the test results for free thyroid-stimulating hormone T4 during pregnancy?

When it comes to endocrinological examination of a pregnant woman, the doctor must be especially careful. The hormonal background of the expectant mother changes significantly. This applies not only to sex hormones, but also to pituitary and thyroid hormones.

In the process of gestation, the level of thyroid-stimulating hormone, as a rule, decreases. The essence of this phenomenon is as follows: a special organ develops within the uterus - the placenta. It is capable of producing a specific active substance hCG (human chorionic gonadotropin). Its mechanism of action is similar to the principles of thyroid-stimulating hormone. It also stimulates more intensive production of active substances in the thyroid gland. It is for this reason that the synthesis of TSH falls. If the intensity of the production of the pituitary active substance remains at the same level, the thyroid gland will secrete an excessive number of thyroid hormones into the blood, and hyperthyroidism will occur. For this reason, when assessing the degree of concentration of thyroid-stimulating hormone in the venous blood of a pregnant woman, it is necessary to take a decrease in the TSH level as normal.

During the period of gestation, this hormone is in an unstable state, and its synthesis depends on the intensity of the production of hCG. In this regard, the level of free tetraiodothyroxine (T4 hormone) becomes an especially important indicator. It is on it that it is necessary to determine the presence of pathological processes with the thyroid gland in pregnant women.

The classic picture of a normal pregnancy is pituitary thyroid stimulating hormone below the established limit, free tetraiodothyronine is within normal limits.

If thyroxine is outside the upper limit, but insignificantly, this can be considered as a variant of the norm. But the same may indicate the onset of thyroid disease. For clarification, it is necessary to conduct a set of additional examinations.

In the case when the T4 level is significantly exceeded, and against the background of this there is an increase in the content of triiodothyronine in the blood (maybe separately or both at once), treatment should be started immediately and the hormones should be brought back to normal.

It makes no sense to prescribe a pregnant woman to perform an analysis for associated (general) tetraiodothyronine. During gestation, the concentration of a special transport protein that binds the hormone increases. Therefore, almost always this indicator will be outside the normal range, but this increase will not have any diagnostic value. But the excess of the TSH concentration norm during the period of gestation indicates serious problems. This situation can adversely affect both the health of the mother and the health of the unborn child.

An excess of the level of thyroid-stimulating hormone indicates a lack of thyroid substances. To make the thyroid gland work more actively, the pituitary gland sends a chemical signal to the organ. With prolonged excess of TSH, the maternal iron may undergo diffuse and nodular changes. The organ will begin to change and grow in order to capture the required amount of iodine salts, but the degree of synthesis will not increase. The state of hypothyroidism will remain. The child's body will also suffer, since the nervous system, headed by the brain, cannot form normally in conditions of a lack of iodine-containing hormones.

According to research data, pregnancy with an extremely low concentration of specific substances of the thyroid gland most often ends in miscarriage. A child who has been born with severe excess TSH levels may be born with mental disabilities. However, this situation can be easily changed and the hormonal status of a pregnant woman can be brought back to normal by taking synthetic hormonal drugs.

Sometimes doctors strongly recommend artificially terminating a pregnancy due to perceived threats to the child's intellectual development. As statistics and medical practice show, in the 21st century it is almost impossible to give birth to a mentally disabled child due to a lack of TSH. In no case should you terminate a pregnancy. The doctor who makes such recommendations is clearly insufficiently qualified.

Thus, when conducting an analysis, the purpose of which is to assess the general state of the thyroid gland, it is necessary to investigate not only specific substances, but also those that have a direct effect on the functioning of the organ: the pituitary hormone TSH and antibody proteins. The thyroid gland performs the basic function necessary for the normal and stable functioning of the whole organism.

Tests vary depending on the suspected disease. In one case, it is necessary to test the blood for some antibodies, in the other case, for others. Some substances act as tumor markers, but it is worth donating blood to determine their level only in a few limited cases, and the results are interpreted ambiguously.

The times of normalization of indicators of hormonal blood tests are long gone. The norms are calculated by various clinics independently, based on the equipment used, chemical reagents and their own methods. Therefore, in each clinic, the result will be different. Trying to interpret the results of different clinics on an equivalent basis is an empty matter, since these indicators cannot be recalculated.

Some standards, from which specialists are based, still exist, and they are enshrined in medical documentation on a worldwide scale. Only a doctor can correctly decipher and interpret the descriptions of laboratory tests. The patient himself runs the risk of making a mistake, making himself a wrong diagnosis and causing great harm to his body by resorting to self-medication.

Taking tests for thyroid hormones does not require any preparation or adherence to special rules. All the information on this matter on the network is nothing more than an invention or delusion of the average graphomaniac without medical education. When a pregnant patient turns to an endocrinologist, it is important to remember that in this state, the hormonal background changes dramatically, and a special approach to blood testing is required.

The author of the article: Kuzmina Vera Valerievna | Endocrinologist, nutritionist

Education: Diploma of the Russian State Medical University named after NI Pirogov with a degree in General Medicine (2004). Residency at Moscow State University of Medicine and Dentistry, diploma in Endocrinology (2006).