Blood test for thyroid hormones: preparation, how to pass correctly

Patients often ask: why does the doctor prescribe thyroid hormone tests? Is an ultrasound scan not enough? Do all hormones need to be tested, or is just one enough?

The point is that even the slightest disruption of thyroid function can lead to serious problems. A blood test will optimally complement the information obtained during an ultrasound scan, which will allow the doctor to prescribe a more effective treatment.

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Indications for analysis

In what cases may a doctor recommend a thyroid hormone test:

• if a person has symptoms that indicate hypo or hyperthyroidism;
• to control the dynamics of hypothyroidism, diffuse toxic goiter;
• in case of delayed mental or sexual development of children;
• in case of cardiac arrhythmia of unknown origin;
• in case of baldness;
• with a sharp change in body weight;
• with a sharp increase in appetite;
• in case of reproductive dysfunction;
• in case of menstrual cycle disorders (in the absence of a monthly cycle );
• for male impotence, impaired libido;
• after an ultrasound scan in the presence of nodes and other formations.

Preparation

In order for the results of thyroid hormone tests to be as accurate as possible, you need to approach the issue of diagnostics with full responsibility and prepare for it correctly.

Doctors suggest that you familiarize yourself with the main instructions, which contain the basic stages of preparation for the test:

1. 2-3 days before the examination, you should limit physical activity and avoid intense sports.
2. A day before the diagnosis, you should give up cigarettes and alcohol; it is also undesirable to visit a bathhouse or sauna, or to overcool.
3. If at the time of the analysis the patient is undergoing treatment with any medications (including iodine-containing and hormonal), then there is no need to refuse to take them. It is enough to simply warn the laboratory specialist about what medications are being taken: a corresponding entry will be made in the form, and the test results will be considered taking into account the adjustments for the medication.
4. It is preferable to donate blood on an empty stomach (preferably in the morning). If the study is conducted at another time of day, it is advisable not to eat for 6-8 hours before donating.

By the way, many modern laboratories working with ultra-precise equipment and the latest generation of reagents do not insist on following any rules for preparing for the analysis. Experts assure that the degree of error in all cases will be insignificant. Therefore, before going to donate blood, it is advisable to clarify the degree of preliminary preparation required in a particular laboratory.

Diet before thyroid hormone tests

A special diet is usually not required before the thyroid hormone test. In some cases, specialists may announce the following conditions:

• It is advisable to exclude alcohol, caffeine, and limit consumption of sweets the day before the test;
• It is not advisable to consume seaweed, sea fish, or caviar the day before the test.

Such conventions are increasingly rarely indicated in the instructions for preparing patients for blood tests. Modern precise diagnostic methods are capable of producing results with minimal permissible error and without observing the listed rules.

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What distorts thyroid hormone tests?

The following factors can have a negative impact on the results:

• smoking before diagnosis, alcohol consumption;
• severe stress, fear, excessive physical exertion before diagnosis;
• too strict a diet over a long period of time.

Upon arrival at the laboratory, you need to sit in the corridor for a few minutes, calm your breathing. Only then should you enter the office.

Technique for performing blood tests for thyroid hormones

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

If the puncture is performed correctly, the risk of complications is minimized. For example, if the blood sampling technique is violated, a through-and-through damage to the vessel with subsequent formation of a hematoma is possible. And if antiseptic requirements are not met, an inflammatory process may begin.

This is why blood sampling must be carried out by a specialist under appropriate conditions, using a disposable syringe or a special vacuum system.

Many clinical institutions still use a needle to directly transfer material into a test tube. This method is not only inconvenient, but also unsafe, as it is associated with an increased risk of blood contact with the environment.

Taking 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 collecting venous blood. The device for conducting the analysis consists of a test tube with a vacuum and a special chemical reagent inside, as well as a thin needle and a holding adapter. Such devices are durable. They completely eliminate the possibility of confusion in the analysis, contact of the material with the environment and the hands of a health worker, and do not require the use of additional tools. Blood collection using this method is painless, safe and fast.

What tests are taken for thyroid hormones?

• TSH (more fully called thyroid stimulating hormone, or thyrotropin) 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 pituitary gland is not impaired, the TSH level decreases against the background of increased thyroid function, and increases against the background of weakened function.
• Free T3 (another name is free triiodothyronine) is a substance synthesized by the thyroid gland that stimulates metabolic processes and activates oxygen absorption in tissues.
• Free T4 (we are talking about free thyroxine) is a hormonal substance produced by the thyroid gland and activating protein synthesis processes.
• AT-TG (meaning the presence of antibodies to thyroglobulin) - the level of these antibodies allows us to detect autoimmune pathologies of the thyroid gland, such as Hashimoto's disease, diffuse toxic goiter, atrophic autoimmune thyroiditis.
• AT-TPO (the presence of microsomal antibodies, or antibodies to thyroid peroxidase) - this refers to the presence of antibodies to the enzyme substance of the gland cells. This analysis is very important for the diagnosis of autoimmune pathologies.

On what day of the cycle should TSH be taken?

The monthly cycle of female patients has no effect on the degree of production and concentration of thyroid hormones. Therefore, it does not matter on what day of the cycle a woman comes to take the test. Patients of any gender are allowed to give blood for the amount of hormones and antibodies on any convenient day.

How is a thyroid hormone test performed?

The material is collected as follows:

1. The health worker prepares instruments, laboratory directions (labels, enters information about the patient, makes notes in the journal and/or electronic system).
2. The patient sits down on a chair. The health worker fixes his arm, first turning the palm upward and maximally straightening the elbow joint. For convenience, a special roller is placed under the elbow area.
3. Apply a tourniquet to the area of the middle third of the shoulder (while the pulse impulses on the wrist should be palpable).
4. The specialist treats the skin in the elbow area with alcohol, asks the patient to make several movements, clenching and unclenching the fist (this will allow the vein to be filled with blood as much as possible), after which the patient fixes the fist in a clenched position.
5. The health worker punctures the vein (the acute angle must be maintained) and collects the material in a test tube or special system, simultaneously loosening the tourniquet. At this time, the patient loosens his fist.
6. The specialist applies a cotton pad soaked in alcohol to the puncture site and removes the needle from the vessel. If a vacuum system was used, the blood tube is first disconnected.
7. The patient should sit for some time with the arm bent at the elbow joint to prevent bleeding. Usually 5-6 minutes is enough for this.

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

Thyroid hormone test for a child

Fluctuations in thyroid hormone levels in childhood are quite common. Statistics show that one baby out of five thousand born babies has a congenital thyroid pathology.

With a deficiency of thyroid hormones, children may lag behind in development, so doctors often prescribe special diagnostics to detect the problem in a timely manner.

The normal TSH level in a child is always higher than in an adult. This hormonal substance is produced by the pituitary gland and serves as a kind of stimulator of the synthesis of T3 and T4. Accordingly, immediately after birth, its level is higher than in adolescence.

At different age periods, normal TSH levels for children differ significantly:

• 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.

The levels of T4 and T3 remain stable throughout the entire period from neonatal to puberty (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 with normal TSH values.

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

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Thyroid hormone tests for men

Hormonal tests are most often required for men if a married couple is unable to conceive a child. It is important to know not only the levels of sex hormones, but also the thyroid hormone levels.

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

• in the presence of nodes or neoplasms in the thyroid gland;
• in case of weight loss or, conversely, sudden weight gain;
• with a sharp increase in appetite;
• with persistent sore throat, weakness, irritability;
• for arrhythmia not associated with heart disease.

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

• TSH – from 0.4 mIU/liter to 4.0 mIU/liter;
• T3 total – from 1.2 nmol/liter to 2.2 nmol/liter;
• Free T3 – from 2.6 lmol/liter to 5.7 lmol/liter;
• T4 total – from 54 nmol/liter to 156 nmol/liter;
• Free T4 – from 9.0 lmol/liter to 22.0 lmol/liter;
• AT-TPO – from 0 to 5.6 U/ml;
• AT-TG – from 0 to 18 U/ml.

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Thyroid hormone test for pregnant women

Thyroid dysfunction in the expectant mother can negatively affect the course of pregnancy and labor. If a woman has hypothyroidism, she is considered to be at risk for miscarriage. There is also a high probability that the child will also have thyroid problems. And, as is known, hypothyroidism in a baby can cause a disruption of his general condition, weak immunity, and slow mental and physical development.

As a rule, a pregnant woman is routinely prescribed an analysis of T3 and T4 levels. The fact is that the TSH indicator during pregnancy is most often within the normal range (due to the increased content of somatotropic hormone, which stimulates the production of TSH).

In case of thyroid disease, tests are repeated every month. Additionally, 1-2 times during pregnancy, an ultrasound examination of the thyroid gland, ECG, and analysis of antibodies to TG and TPO are performed.

Normal thyroid function indicators during pregnancy are as follows:

• TSH – from 0.4 to 4.0 μIU/ml;
• Total T3 – from 1.3 to 2.7 nmol/liter;
• Free T3 – from 2.3 to 6.3 pmol/liter;
• Total T4 – from 100 to 209 nmol/liter in the first trimester, from 117 to 236 nmol/liter in the second and third trimesters;
• Free T4 – from 10.3 to 24.5 pmol/liter in the first trimester, from 8.2 to 24.7 pmol/liter in the second and third trimesters.

It should be noted right away that reference values for various 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 normal variants.

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Antibodies

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

The fact is that an increase in the concentration of the antibodies presented indicates the presence of certain autoimmune processes in the gland. Such an analysis is not taken without indications: it is prescribed if the fact of autoimmune pathology has already been proven.

For the patient, a change in the antibody level is unlikely to be informative in principle. After all, an increase in the level of AT-TPO and AT-TG is not considered separately, but in combination with other indicative changes. Thus, an increase in their content against the background of a normal TSH value does not indicate the presence of pathology.

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Hormonal Tests After Thyroid Removal

After the operation of complete removal of the thyroid gland (such intervention is called thyroidectomy), the production of thyroid-stimulating hormones completely stops. As a result, the pituitary gland begins to work at an increased rate, trying to replenish adequate hormonal levels. At this stage, it is very important to start taking thyroxine so that complications such as thyroid comatose state do not develop. The first symptoms of such a condition may be:

• apathy, constant drowsiness, clouding of consciousness;
• decrease in body temperature;
• attacks of cold sweating;
• bradycardia, muscle atony;
• memory impairment;
• problems with kidney function;
• decreased intestinal motility.

The symptoms voiced do not appear immediately, but gradually. Therefore, taking thyroxine after surgery is mandatory. The patient should periodically take a blood test for TSH levels.

Low TSH levels after thyroid removal may indicate taking excessively high doses of thyroxine, or a functional failure of the pituitary-hypothalamus system in the brain.

High TSH levels after thyroidectomy indicate excessive TSH production – for example, in disorders of endocrine function, during treatment with certain drugs (antiemetics, antiepileptic drugs, prednisolone, cardiac glycosides, morphine-containing drugs, oral contraceptives).

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How long does it take to test thyroid hormones?

The period during which you can receive the results of the thyroid hormone test may vary. First of all, it depends on the capabilities of the laboratory itself. For example, in a state clinic, the procedure may take several days - for example, when using outdated equipment with first or second generation analyzers. And in a paid network of laboratories, the result can be obtained in a day: they usually use the latest analyzers that provide a quick and accurate result. On average, it is considered that the study from the moment of blood sampling until the results are issued can last from 1-2 to 6-7 days. It is better to inquire about the exact period in the specific laboratory where the diagnostics will be carried out.

What does a thyroid hormone test show?

Based on the results of thyroid hormone tests, it is possible to judge the increase or decrease in the production of such substances as triiodothyronine, thyroxine, and thyroid-stimulating hormone. Any significant change in the level of these hormones indicates a functional disorder of the organ, which can be characterized by two types:

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

Many processes inside the body depend on the mode in which the gland operates. These include general metabolism, fat, protein and carbohydrate metabolism, heart function, the quality of blood vessels, as well as digestive, mental and reproductive functions.

Thus, the thyroid hormone test will be able to provide an answer to the causes of many health problems. The doctor will be able to conduct differential diagnostics, excluding some diseases and confirming others, and also prescribe the correct and effective treatment.

Decoding the analysis of thyroid hormones

Probably, any patient after giving blood for thyroid hormones wants to find out as soon as possible whether everything is in order "there". Of course, it is not entirely reasonable to decipher the analysis results on your own: this should be done by a specialist with both knowledge and experience. Therefore, it is imperative to contact an endocrinologist for clarification.

We will try to answer only the most common questions regarding the options for hormonal changes.

• An elevated TSH value indicates an insufficient thyroid function (hypothyroidism). If there is such a picture: TSH is elevated, T4 is lowered - then a conclusion is made about manifest hypothyroidism. If TSH is elevated, and T4 is normal, then subclinical or latent hypothyroidism is suspected. With high TSH, the patient usually complains of constant fatigue, cold extremities, drowsiness, deterioration of the nails and hair.
• If TSH is normal and T4 is low (!), you should definitely take the test again (preferably in another laboratory). Such a picture is observed only in a few cases: with a laboratory error, with early manifestations of autoimmune thyroiditis, and also with an overdose of antithyroid drugs in patients with diffuse toxic goiter.
• The following combinations of indicators also indicate a laboratory error:
  • normal TSH against the background of reduced T3;
  • normal TSH against the background of normal T4 and reduced T3;
  • normal TSH against the background of elevated T4 and T3.
• A decrease in TSH values occurs with an excess of hormones. With low TSH and high T4 (or T3), it makes sense to talk about manifest thyrotoxicosis. If TSH is low, and T4 and T3 are within normal limits, then this indicates latent thyrotoxicosis.

Both overt and latent thyrotoxicosis are diseases that cannot be left untreated. It should also be remembered that during pregnancy, a physiologically conditioned decrease in TSH is often observed, which is not related to pathology.

Thyroid hormone tests for hypothyroidism

When hypothyroidism is suspected, most medical professionals focus on TSH levels. The hormone produced by the pituitary gland "tells" the thyroid gland how many hormones have been produced. So, if TSH increases, it means that the pituitary gland is stimulating the thyroid gland to produce thyroid hormones, and vice versa. If TSH levels are low, hypothyroidism may be suspected.

It is important to take into account that in the morning the TSH level is usually stable, closer to midday it decreases, and in the evening it increases.

At the diagnostic stage, if hypothyroidism is suspected, the T4 level is also determined: the analysis will help to assess the actual content of thyroid hormones in the bloodstream. In terms of its information content, the T4 analysis is somewhat inferior to the TSH analysis. The fact is that the level of total T4 depends on the number of binding proteins. And their content is affected by liver and kidney diseases, as well as the state of expectation of a child in women. Nevertheless, a low concentration of total T4 in most patients still signals hypothyroidism. Free T4 is more informative than total T4. It determines the amount of free thyroxine in the bloodstream. Therefore, its low content is an indication of the presence of hypothyroidism.

Total T3 is the active form of the hormone produced by the thyroid gland. Its level can neither confirm nor deny the presence of hypothyroidism. But this value is often used to clarify the diagnosis in general.

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Bad Thyroid Hormones Test Results: Should You Panic?

Blood tests for thyroid hormones can be taken in almost every medical diagnostic laboratory today. At the same time, prices for the test vary in different laboratories, sometimes even significantly. Experts say: you shouldn’t look for the lowest price, because the quality of the final result often suffers from this: the patient receives frankly “bad” results, worries, and gets stressed. But in reality, it turns out that the result is simply incorrect – due to some laboratory error. Why can this happen?

In medicine, three generations of analyzers are used that can analyze blood for hormone levels. The first generation does not need much mention: it is almost never found in diagnostic institutions. Second-generation analyzers provide for the use of enzyme immunoassay: this method is quite cheap, easy to use, and can “work” with inexpensive domestic reagents. The cost of such an analysis is usually low, but the accuracy of the results can be “lame”: the error can reach 0.5 μIU/ml, which is definitely a lot. If we consider that the error in third-generation analyzers is only 0.01 μIU/ml, we can draw the corresponding disappointing conclusions.

If you are going to the lab to have your blood drawn, or have already taken the results that seemed "bad" to you, inquire about the exact method by which the blood test for thyroid hormones will be performed. Modern analyzers, belonging to the third generation, provide clear information about the hormonal level, and the analysis itself is done in 1-2 days.

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