Blood test for thyroid hormones: how to properly prepare

Often, patients ask: why does the doctor prescribe thyroid hormone tests? Is ultrasound not enough? Do all hormones need to be checked, or is there enough of one?

The bottom line is that even the slightest glitches of the functionality of the thyroid gland can lead to serious trouble. A blood test will optimally supplement the information obtained by ultrasound, which will allow the doctor to prescribe more effective treatment.

[1], [2], [3], [4]

Indications for analysis

When can a doctor recommend testing for thyroid hormones:

• if a person has symptoms indicating the presence of hypo or hyperthyroidism;
• to control the dynamics of hypothyroidism, diffuse toxic goiter;
• at belated mental or sexual child development;
• for violations of the heart rhythm of an unknown origin;
• with baldness;
• with a sudden change in body weight;
• with a sharp increase in appetite;
• at violation of reproductive function;
• with violations of the menstrual cycle (in the absence of a monthly cycle);
• with male impotence, impaired libido;
• after conducting ultrasound in the presence of nodes and other formations.

Preparation

In order to ensure that the results of thyroid hormone assays are extremely accurate, it is necessary to approach the issue of diagnostics with all responsibility and correctly prepare for it.

Doctors offer to familiarize themselves with the basic instruction containing the basic stages of preparation for the analysis:

1. 2-3 days before the study you need to limit physical activity, avoid intensive sports.
2. The day before the diagnosis you need to give up cigarettes and alcohol; It is also undesirable to visit a sauna or a sauna, to be supercooled.
3. If at the time of the analysis the patient is treated with any medications (including iodine and hormonal), then you do not need to refuse to take them. It is enough just to warn a laboratory specialist about what preparations are being taken: a record will be made on the form and the results of the analysis will be considered taking into account the amendments to the medication.
4. Blood is preferable to take on an empty stomach (better - in the morning). If the study is carried out at other times of the day, it is advisable not to take food for 6-8 hours before delivery.

By the way, many modern laboratories working with ultra-precise equipment and reagents of the latest generation do not insist on observing any rules of preparation for the analysis. Experts assure that the degree of error in all cases will be of little significance. Therefore, before going for blood donation, it is desirable to clarify the degree of pre-training required in a particular laboratory.

Diet before thyroid hormone tests

A special diet on the eve of the analysis of thyroid hormones is most often not required. In some cases, specialists can voice such conditions:

• a day before the analysis it is desirable to exclude alcohol, caffeine, limit the use of sweets;
• on the eve of delivery it is undesirable to use seaweed, sea fish, caviar.

Such conventions are less often indicated in the instructions for preparing patients for blood tests. Modern accurate diagnostic methods are able to produce results with a minimum permissible error and without observing the listed rules.

[5]

What does the analysis of thyroid hormones distort?

A negative impact on the results can have such factors:

• smoking before the diagnosis, drinking alcohol;
• severe stress, fear, excessive exercise before diagnosis;
• too hard diet for a long period of time.

Upon arrival in the laboratory, you need to sit in the corridor for a few minutes, to calm your breathing. Only after this should go into the office.

The technique of blood test for thyroid hormones

On how correctly the blood test for thyroid hormones will be taken, the result will largely depend on it. As a result, a correct diagnosis will be made, and correct treatment will be prescribed.

With a competent puncture, the risk of complications is minimized. For example, with a broken blood sampling technique, a through damage to the vessel is possible with the subsequent formation of a hematoma. And if the antiseptic requirements are not observed, the inflammatory process may begin.

That is why blood sampling should be performed by a specialist under the proper conditions, using a disposable syringe or a special vacuum system.

Many clinics still use a needle to directly transfuse the material into a test tube. This technique is not only inconvenient, but also unsafe, because it is associated with an increased risk of blood contact with the environment.

Taking a material with a disposable syringe is also considered a relatively outdated method. The obvious disadvantages of this procedure are the need for additional test tubes and test systems, as well as frequent cases of hemolysis during manipulation.

Modern laboratories have long been using new vacuum devices for venous blood sampling. The device for analysis consists of a tube, inside of which there is a vacuum and a special chemical reagent, and also from a thin needle and a retaining adapter. Such devices are strong. They completely exclude the possibility of confusion in the analyzes, contact of the material with the environment and the hands of the health worker, and do not require the use of additional instruments. Blood sampling using this technique is painless, safe and fast.

What tests are given for thyroid hormones?

• TTG (more fully it is called thyrotropic hormone, or tiroropin) is a substance produced by the pituitary gland. It activates the formation and production of hormones in the thyroid gland (such as T3 and T4). When the work capacity of the pituitary gland is not broken, the level of TSH decreases against the background of the strengthening of the thyroid function, and increases with the weakening of its function.
• T3 free (another name is free triiodothyronine) is a substance synthesized by the thyroid gland that stimulates metabolic processes and activates oxygen uptake in tissues.
• T4 free (it is a question of free thyroxine) is a hormonal substance produced by the thyroid gland and activating the processes of protein synthesis.
• AT-TG (meaning the presence of antibodies to thyroglobulin) - the level of these antibodies can detect autoimmune thyroid gland pathologies, such as Hashimoto's disease, diffuse toxic goiter, atrophic autoimmune thyroiditis.
• AT-TPO (the presence of microsomal antibodies, or antibodies to thyroid peroxidase) - we are talking about the presence of antibodies to the enzyme substance of the gland cells. This analysis is very important for the diagnosis of autoimmune pathologies.

In what day of a cycle to hand over TTG?

The monthly cycle in female patients has no effect on the degree of production and the concentration of thyroid hormones. Therefore, it does not matter in which day of the cycle a woman will come for the analysis. Blood for the number of her hormones and antibodies is allowed to be given to patients of any gender on any convenient day.

How is thyroid hormone analysis taken?

The material is taken in the following way:

1. The paramedic prepares instruments, laboratory direction (marks, brings information about the patient, makes notes in the journal and / or the electronic system).
2. The patient sits down on a chair. The paramedic fixes his hand, first turning his palm upward and maximally unbending the elbow joint. For convenience, a special roller is placed under the elbow area.
3. Imposes a tourniquet in the zone of the middle third of the shoulder (with pulse impulses on the wrist should be palpated).
4. The specialist treats the skin with alcohol in the elbow area, asks the patient to make several movements, clenching and unclenching the fist (this will allow the blood to fill the vein), after which the patient fixes the fist in the clamped state.
5. The paramedic punctures the vein (you should withstand an acute angle) and picks up the material in a test tube or special system while weakening the tourniquet. The patient at this time weakens the fist.
6. The specialist applies a wadded disk moistened with alcohol to the puncture site and extracts the needle from the vessel. If a vacuum system was used, the tube with blood is previously disconnected.
7. The patient should sit for a while, bending his arm in the elbow joint to avoid bleeding. Usually it takes 5-6 minutes.

The health worker puts the signed test tubes in a special container, and then sends them to the laboratory.

Analysis for thyroid hormones to a child

The fluctuations in the level of thyroid hormones in childhood are quite common. Statistics states that one child of five thousand babies born has a congenital thyroid pathology.

With a deficiency of thyroid hormones, children may lag behind in development, so doctors often prescribe a special diagnosis to timely identify trouble.

The normal index of TTG in a child is always higher than that of an adult. This hormonal substance is produced by the pituitary gland and serves as a kind of stimulant for the synthesis of T3 and T4. Accordingly, immediately after birth, his level is higher than in adolescence.

In different age periods, the normal TSH for children is significantly different:

• the first three days after the birth of the baby - from 1.3 to 16 mm / l;
• during the first four weeks of life - from 0.9 to 7.7 mm / l;
• after seven years and older - from 0.6 to 5.5 mm / l.

Levels of T4 and T3 remain stable throughout the period from neonatal to maturity (2.6-5.7 pmol / l and 9-22 pmol / l, respectively).

At the first signs of hypothyroidism there is a decrease in the content of T4 and T3 at normal TSH values.

Secondary hypothyroidism occurs when the pituitary gland is damaged: all kinds of metabolism in the body are disrupted, the child becomes uncommunicative, apathetic, lags behind in development - not only mentally, but also physically. The use of hormonal drugs at an early stage of pathology makes it possible to stabilize metabolic processes and stimulate the development of the baby.

[6], [7], [8], [9], [10], [11], [12]

Analyzes for thyroid hormones in men

Analyzes of hormones to men often have to take in the event that a married couple can not conceive a child. It is important to know not only the levels of sex hormones, but also the content of thyroid hormones.

In addition to reproductive problems, blood sampling for analysis can be recommended in the following cases:

• in the presence of nodes, neoplasms in the thyroid gland;
• at emaciation or, conversely, a sharp set of weight;
• with a sharp increase in appetite;
• with impassable perspiration in the throat, weakness, irritability;
• with arrhythmia, not associated with heart disease.

Normal levels of hormones in the blood in men are the same as in adult women:

• TSH - from 0,4 mED / liter to 4,0 mU / liter;
• T3 total - from 1.2 nmol / liter to 2.2 nmol / liter;
• T3 free - from 2.6 lmol / liter to 5.7 lmol / liter;
• T4 total - from 54 nmol / liter to 156 nmol / liter;
• T4 free - from 9.0 lmol / liter to 22.0 lmol / liter;
• AT-TPO - from 0 to 5.6 Ed / ml;
• AT-TG - from 0 to 18 Ed / mL.

[13], [14]

Analysis for thyroid hormones in pregnant women

Dysfunction of the thyroid gland in a future mother can adversely affect the course of pregnancy and labor. If a woman has hypothyroidism, then she is considered to be at risk for miscarriage. There is also a high probability that the child born will also have problems with the thyroid gland. And, as you know, hypothyroidism in a baby can cause a violation of his general condition, weak immunity, slowing mental and physical development.

As a rule, the pregnant woman is routinely assigned the analysis of T3 and T4 levels. The fact is that the TTG index during pregnancy is most often within normal limits (due to the increased content of growth hormone, which stimulates the production of TSH).

When the thyroid gland is diagnosed, the tests are repeated every month. In addition, 1-2 times per pregnancy, ultrasound examination of the thyroid gland, ECG, analysis of antibodies to TG and TPO.

The normal parameters of the thyroid gland during pregnancy are as follows:

• TTP - from 0.4 to 4.0 μM / mL;
• T3 total - from 1.3 to 2.7 nmol / liter;
• T3 free - from 2.3 to 6.3 pmol / liter;
• T4 total - from 100 to 209 nmol / liter in the first trimester, from 117 to 236 nmol / liter in the second and third trimesters;
• T4 free - from 10.3 to 24.5 pmoles / liter in the first trimester, from 8.2 to 24.7 pmoles / liter in the second and third trimesters.

It should immediately be noted that the reference values of different hormones may differ slightly in different laboratories. The fact is that when working with biomaterial, a large number of reagents are used, which determine the variants of the norm.

[15], [16], [17], [18], [19], [20],

Antibodies

Many patients want to clarify: why does the thyroid hormone test contain information not only about hormones themselves, but also about some unknown antibodies? For what the doctor information about the so-called AT-TPO and AT-TG?

The fact is that an increase in the concentration content of the presented antibodies indicates the presence in the gland of certain autoimmune processes. Without testimony, such an analysis does not pass: it is prescribed if the fact of an autoimmune pathology has already been proven.

For a patient, changing the level of antibodies in principle is unlikely to become informative. After all, the increase in the level of AT-TPO and AT-TG is not considered separately, but in combination with other demonstrative changes. So, the increase in their content against the background of a normal TSH value does not indicate a pathology.

[21], [22], [23]

Analyzes for hormones after removal of the thyroid gland

After the operation of complete removal of the thyroid gland (such an intervention called thyroidectomy), the production of thyroid-stimulating hormones completely stops. As a consequence, the pituitary gland starts to work at an accelerated pace, trying to fill an adequate hormonal level. At this stage it is very important to start taking thyroxine, so that complications in the form of a thyroid comatose state do not develop. The first symptoms of this condition can be:

• apathy, persistent drowsiness, confusion;
• lowering of body temperature;
• attacks of cold sweating;
• bradycardia, muscle atony;
• memory impairment;
• problems with kidney function;
• decreased intestinal motility.

The sounded symptomatology does not appear immediately, but gradually. Therefore, the administration of thyroxine after the operation is mandatory. Periodically, the patient must take a blood test to the level of TSH.

Low TSH level after removal of the thyroid gland can talk about taking unnecessarily high doses of thyroxine, or about functional failure of the pituitary-hypothalamus system in the brain.

The high TSH content after thyroidectomy indicates the excessive production of TSH - for example, in disorders of the endocrine function, in the treatment of certain drugs (antiemetic, antiepileptic drugs, prednisolone, cardiac glycosides, morphine-containing drugs, oral contraceptives).

[24], [25], [26]

How much analysis is done for thyroid hormones?

The period for which it will be possible to obtain the results of the analysis for thyroid hormones may be different. First of all, it depends on the capabilities of the laboratory itself. For example, in the state polyclinic, the procedure can take several days - for example, when using outdated equipment with analyzers of the first or second generation. And in a paid network of laboratories the result can be obtained in a day: they usually use the latest analyzers, which provide a quick and accurate result. On average, it is believed that the study from the time of taking the blood to the delivery of results on the hands can last from 1-2 to 6-7 days. About the exact period it is better to take an interest in a specific laboratory, in which the diagnosis will be carried out.

What does the thyroid hormone test show?

On the basis of effective information on thyroid hormone tests, one can judge whether the production of such substances as triiodothyronine, thyroxine, thyroid-stimulating hormone increases or decreases. Any significant change in the level of these hormones indicates a violation of the functionality of the organ, which can be characterized by two types:

• Hyperthyroidism (this variant is also called thyrotoxicosis) indicates an increased production of hormonal substances by the thyroid gland;
• Hypothyroidism indicates a decreased production of hormonal substances by the thyroid gland.

On the one of the modes of iron, many processes inside the body depend. This is a common metabolism, fatty, protein and carbohydrate metabolism, the work of the heart, the quality of the vessels, as well as digestive, mental and reproductive function.

Thus, an analysis of thyroid hormones can give an answer about the causes of many health problems. The doctor will be able to conduct differential diagnosis, excluding certain diseases, and confirming others, and also to appoint a correct and effective treatment.

Transcript of thyroid hormone assay

Probably, any patient after donating blood to the thyroid hormones as soon as possible strive to find out whether everything is "there" in order. Of course, it is not entirely reasonable to conduct an independent interpretation of the analyzes: it must be done by a specialist endowed with both knowledge and experience. Therefore, it is necessary to consult a doctor-endocrinologist for explanations.

We will try to answer only the most common questions regarding the variants of hormonal changes.

• The elevated TSH value indicates an insufficient function of the thyroid gland (hypothyroidism). If there is such a picture of TSH elevated, T4 is lowered - then they place the conclusion of manifest hypothyroidism. If TTG is elevated, and T4 is normal, subclinical, or latent hypothyroidism is suspected. At high TSH the patient usually complains of constant fatigue, cold extremities, drowsiness, deterioration of a condition of fingernails or nails and hair.
• At normal TTG and reduced T4 (!) It is necessary to hand over the analysis repeatedly (it is better - in other laboratory). A similar picture is observed only in a few cases: with a laboratory error, with early manifestations of autoimmune thyroiditis, and with an overdose of thyreostatic drugs in patients with diffuse toxic goiter.
• The laboratory error is also indicated by such combinations of indicators as:
  • normal TTG against a background of low T3;
  • normal TTG on a background normal T4 and lowered T3;
  • normal TTG on the background of elevated T4 and T3.
• The decrease in TSH values occurs with an excessive amount of hormones. With low TSH and high T4 (or T3), it makes sense to talk about the manifestation of thyrotoxicosis. If TTG is low, and T4 and T3 are within normal limits, then this indicates a latent thyrotoxicosis.

Both overt and covert thyrotoxicosis are diseases that can not be left untreated. Also, one should not forget that during pregnancy, a physiologically conditioned decrease in TSH is often observed, which does not pertain to pathology.

Analyzes for thyroid hormones in hypothyroidism

If hypothyroidism is suspected, most medical specialists emphasize TSH levels. Pituitary-synthesized hormone "tells" the thyroid gland of how many hormones are produced. So, if the TSH rises, it means that the pituitary gland gives an incentive to the thyroid gland to develop thyroid hormones, and vice versa. With a lowered TSH level, hypothyroidism can be suspected.

It should be borne in mind that in the morning the level of TTG is more often stable, closer to noon it goes down, and by evening - it rises.

At the diagnostic stage, when suspicion of hypothyroidism is also determined by the T4 level: the analysis will help to assess the actual content of thyroid hormones in the bloodstream. By its informative analysis on T4 is somewhat inferior to the analysis on TTG. The fact is that the T4 level is generally dependent on the number of binding proteins. And their content is affected by liver and kidney disease, as well as the state of expectation of the child in women. Nevertheless, the low concentration of T4 in the majority of patients still signals hypothyroidism. More informative than T4 common, is T4 free. It is he who determines the number of free thyroxine in the bloodstream. Therefore, its small content is an indication of the presence of hypothyroidism.

T3 is the active form of the hormonal substance synthesized by the thyroid gland. His level can neither confirm nor disprove the presence of hypothyroidism. But this value is often used to clarify the diagnosis as a whole.

[27], [28], [29]

Bad tests for thyroid hormones: is it worth it to panic?

A blood test for thyroid hormones can be taken today in almost every medical diagnostic laboratory. At the same time in different laboratories the prices for carrying out the research differ, and sometimes even significantly. Experts argue: do not look for the lowest price, because often the quality of the end result suffers: the patient gets frankly "bad" results, experiences, gets stressed. But in fact it turns out that the result is simply wrong - because of some laboratory error. Why this can happen?

In medicine, three-generation analyzers are used that can perform a blood test on the level of hormones. About the first generation can especially not be mentioned: it is almost never found in diagnostic facilities. Analyzers of the second generation include the use of enzyme immunoassay: this method is quite cheap, convenient to use, can "work" with inexpensive domestic reagents. The cost of such an analysis is usually low, but the accuracy of the results can be "limp": the error can reach 0.5 μIU / ml, which is unambiguously large. If we take into account that the error in the third-generation analyzers is only 0.01 μM / ml, we can make the corresponding disappointing conclusions.

If you are going to take blood to the laboratory, or have already taken the results that seemed "bad" to you, ask what method will be used to perform a blood test for thyroid hormones. Modern analyzers relating to the third generation provide clear information about the hormonal level, and the analysis itself is done in 1-2 days.

[30], [31], [32]