Blood test for thyroid hormones: when to pass and how to prepare. The prevalence of thyroid disease is in second place among all diseases of the endocrine system,

Blood test for thyroid hormones: when to pass and how to prepare.

The prevalence of thyroid diseases is in second place among all diseases of the endocrine system, yielding the championship only with diabetes mellitus. Even a slight impairment of the gland greatly worsens the quality of life.

Modern medicine has enough knowledge and ways to prevent such an outcome. For a better result, it is important to identify violations of the gland at an early stage and timely start treatment. If, according to your complaints and inspection data, the doctor suspected the pathology of the thyroid gland, he will send you blood for analysis.

How does the deficiency and excess of the thyroid hormones manifest, under what diseases they arise which rules need to be observed to get a reliable result.

Hormones thyroid gland

• Tireotropic hormone (TSH) It is produced by non-thyroid gland, but a brain, but it is he who controls the work of the thyroid gland and reflects its condition. Control occurs on the principle of negative feedback. If thyroid hormones are not enough, the level of TSH increases, and it is active in stimulating the work of the gland. With their excess, the opposite occurs, the level of TSH decreases, and the production of hormones is weakening.

In the diagnosis of diseases with impaired thyroid function, endocrinologists are most often used by TSH.

• Tyroxin (T4) It is generated by follicular cells of the thyroid gland. Normal is the level of free thyroxine in the blood of 9.0-22.0 pmol / l.
• Triiodothyronine (T3) – Most of this hormone is formed from T4 in the tissues of the body and only about 20% is produced together with T4 in thyroid cells. Triiodothironine is 3-5 times in biologically active thyroxine. Normal is considered the level of free triiodothyronine in blood 2.6-5.7 pmol / l.

You need to know that T4 and T3 can be defined in two different types.

These are fractions of each hormone, common and free. The overall concentration of hormones in the blood may vary depending on the environmental conditions, concomitant states (for example, pregnancy, liver disease), preparations, etc. Related hormones are not active and do not affect well-being. Free T4 and T3 (they are not marked on the letterhead, the letter "C" from the Russian "free" or F from the English Free) is the amount of hormone that is not associated with a special protein. ST3 and ST4 are active hormones, and only they are used to diagnose disorders of the thyroid gland.

When it is necessary to determine the level of hormones.

An increase in the level of thyroid hormones in the blood is called thyrotoxicosis or hyperthyroidism.

Thyrotoxicosis may present with the following symptoms:

• frequent sweating at rest, constant feeling of heat;
• increased excitability of the nervous system;
• tremor (tremor) of the hands;
• heart rate above 90-120 per minute or the appearance of an arrhythmia;
• weight loss with increased appetite;

Decreased levels of thyroid hormones are called Hypothyroidism

Common signs of hypothyroidism

• Dry skin, especially in the elbows; hair loss
• Swelling leading to weight gain
• Constipation.
• Increase in blood cholesterol levels.
• Fatigue, weakness, memory impairment, drowsiness.
• Violation of the menstrual cycle, infertility.
• Violation of libido and discharge from the nipples, regardless of the patient's gender.

The threat of miscarriage, the risk of congenital pathology of the fetus, hypothyroidism is especially dangerous because of the birth of children with a low level of intelligence in the future.

Thyroid function monitoring is necessary if:

• Are you experiencing any of the above symptoms?
• a change in the size or structure of the gland was detected (by palpation or by ultrasound);
• you are planning a pregnancy or are already pregnant;
• in the survey for taking HRT drugs in the menopause.

In addition, it is mandatory to assess the level of TSH in all newborns even in the maternity hospital.

Preparation for the delivery of the analysis

The thyroid gland quickly responds to changes in the living conditions of the body, but firstly, these fluctuations always occur within the normal range, and secondly, a sufficiently long time must pass for changes in hormone levels (for TSH this is 2.5-3 months, for T4 – about 2 weeks). Since the fluctuations of these two indicators are very smooth, special preparation for the analysis is not required. But there are several conditions for obtaining a reliable result.

• When large doses of iodine enter the body, if the analysis is prescribed for examination, but without obvious indications or clinical manifestations, the test should be postponed for about a month. This happens if the patient underwent an x-ray examination with contrast. Also, iodine is absorbed through the skin when treating the surface of the body. Iodine is found in some preparations for temporary use (for example, for the treatment of inflammatory diseases of the genital area or the treatment of the tonsils).

If you need to take the test immediately, then you should warn your doctor about such contact with iodine, since even one drop of iodine can temporarily block the thyroid gland. If the patient is taking vital drugs containing iodine (most often these are antiarrhythmics), then there is no question of canceling. The use of iodized salt, seafood and potassium iodide preparations in physiological dosages does not affect the accuracy of the result.

1. If you are taking thyroxine preparations, then the time of taking the pill will not matter for TSH control, but for ST4 it is huge.Donate blood before taking the pill
2. Some drugs may increase (metoclopramide, clomiphene, carbamazepine, theophylline, and others) or lower (bromocriptine, apomorphine, somatostatin, morphine, glucocorticoids, heparin, and others) TSH levels. If you are taking any of the drugs, see the annotations for the effect of this drug on the endocrine system. And most importantly, do not forget to tell your doctor about taking them, since an altered TSH level may be the result of taking the drug, and not thyroid pathology.
3. It is not necessary to take blood for thyroid hormones on an empty stomach. Food intake does not affect the concentration of hormones in the blood. However, laboratory staff, in order to avoid errors in the methodology, recommend taking tests strictly on an empty stomach. This recommendation in cases of determining TSH, st3 and st4 has no proven grounds, since the increased concentration of blood lipids, which everyone fears, does not affect the operation of modern equipment.

Don't forget to see a doctor

Blood is taken for analysis for thyroid hormones from a vein. The results are usually ready the next day. But, despite the knowledge gained, you should not engage in self-diagnosis, and even more so self-treatment. If something worries you, the best way out is to contact a specialist who, after examination and questioning, will be able to suggest a diagnosis and prescribe the necessary examination. It is extremely rare for a diagnosis to take all hormones, more often only TSH is needed for screening, and TSH and st4 are needed to clarify the diagnosis.

In addition to testing for hormones, your doctor may also refer you to other tests, such as blood tests for antibodies or specific proteins.