A blood test for thyroid hormones , health and disease.Explanation of analysis.- Causes, Symptoms and Treatment .MF .

August 12, 2017 17:52 | The Analysis On Hormones

Donating should be on an empty stomach (do not even drink) blood test for thyroid hormones.Blood is taken from a vein.It is advisable to give blood up to 10 - 10.30.chasov morning.As directed by the physician prior to the study to exclude drugs thyroid hormones.The day before delivery of the analysis to exclude the possibility of training and stress, half an hour before blood sampling is desirable in a calm state.

indicators that are marked for analysis and evaluation of the thyroid gland: T3 (triiodothyronine), total and free T4 (thyroxine) total and free, TSH (thyroid-stimulating hormone pituitary gland), antibodies to thyroglobulin, antibodies to tiroksinperoksidaze), calcitonin.

Early treatment of thyroid disease will help to avoid serious consequences and surgical interventions.It requires early diagnosis of hypothyroidism, as his running form (hypothyroid coma) can lead to irreversible consequences.Diagnosis expressed forms gipotireza does not cause much difficulty.It is more diff

icult to identify mild symptoms are not always typical, particularly in elderly patients.Where it is easy to suspect cardiovascular failure.Kidney and others. The diagnosis of hypothyroidism is specified next to the diagnostic laboratory blood studies on iodine and thyroid hormones (T3, T4, thyroid-stimulating).Functional iron deficiency is characterized by a decrease in iodine content and T3, T4, and increased TSH.

Laboratory diagnosis of thyroid disease

survey thyroid decides today one of the most urgent tasks of medicine: the early detection of prostate dysfunction for effective treatment with the least consequences, both the treatment and pathophysiological disturbances in the body.
To assess the function of the thyroid gland in the laboratory conducted study:
• determination of thyroid hormones
• markers of thyroid disease
• regulating
pituitary hormones - and only the doctor will select the optimal inspection scheme, allowing to obtain sufficient information for the diagnosis and monitoring ofthe patient's thyroid status.


Thyroid-stimulating hormone (TSH) - is the pituitary hormone that, acting on the thyroid gland, plays a major role in ensuring the normal circulating levels iodothyronines, T3 and T4.TSH level is controlled by the hypothalamic hormone TRH (thyrotropin - releasing hormone) and is inversely proportional to the concentrations of T3.
In primary hypothyroidism, when the reduced production of thyroid hormones, the TSH level is usually kept high.On the other hand, the secondary or tertiary hypothyroidism when developing decline due to an impaired thyroid hormone and hypothalamic-pituitary function, TSH level is usually low.In hyperthyroidism, the TSH level is usually reduced (secondary hyperthyroidism cases are extremely rare).

Third Generation TSH

Like the previous test for TSH.But unlike him, it is an order of magnitude greater sensitivity, which allows to determine very low concentrations of TSH with high accuracy.allowing to identify subclinical form of the disease, as well as to conduct a closer monitoring of the therapy.

total T 4

Thyroxine (T4) , the main thyroid hormone, which normally circulates in the amount of approximately 58 - 161 nmol / L (4.5 - 12.5 mg / dl), much of it is tiedwith transport proteins, mainly TBG, condition.Against the background of a normal level of protein binding thyroid hormones, hyperthyroidism is characterized by increased and hypothyroidism - reduced level of circulating T4.However, in patients with abnormal levels of proteins that bind thyroid hormones, such parallelism between the concentration of total T4 and thyroid status is excluded.
Since the level of total T4 often goes beyond the norm in people with euthyroid status or may be normal in disorders of the thyroid gland, is desired rating level of circulating TSH, for example, using the T3 Uptake assay.If any of the functions of the thyroid gland values ​​of total T4 and T3 Uptake would deviate from normal in one direction, whereas the TSH level changes in patients with euthyroid status they would deviate from the norm in opposite directions.The product quantities of T4 and T3 Uptake, divided by 100, known as the index of Free Thyroxine (Free Thyroxine Index FT4I).

Free T4

circulating main thyroid hormone thyroxine (T4) almost all linked to transport proteins, the main of which is thyroxine-binding globulin (TBG), and to maintain a balance between the two so that the change in the level of transport proteins causescorresponding change in total T4 level whereas the level of free T4 remains relatively unchanged.Therefore, it can be expected that the concentration of free T4 is more accurately reflect the clinical thyroid status than the concentration of total T4, because beyond the norm total T4 results may reflect a dysfunction of the thyroid, and simply change (physiological or pathological) level of transport proteins.
For example, the typical rise in TSH during pregnancy, oral contraceptives and estrogen therapy cause a rise in the level of total T4, often above the normal range, without causing a corresponding rise of the level of free T4.In addition, TSH level changes can sometimes hide the dysfunction of the thyroid gland, raising the level of total T4 in patients with hypothyroidism or reducing it in patients with hyperthyroidism to normal values.And in these cases free T4 concentration will also more accurately reflect the true thyroid status than total T4 concentration.

total T3

Under normal physiological conditions, the T3 is about 5% of thyroid hormones in serum.Although T3 concentration lower than the concentration of circulating T4, it has a higher metabolic activity, faster turnaround and high volume distribution.It reported that in some cases, thyrotoxicosis is abnormally high concentrations of T3 play a greater role than the concentration of T4, T3 measurement value increases.In addition, the definition of T3 is an important link in the monitor observation of patients with hypothyroidism receiving sodium liothyronine therapy.Unlike test "T3 Uptake", which estimates the saturation of protein binding of thyroid hormones T3 test actually measures total circulating levels of triiodothyronine.Many reports indicate that there is a clear difference in T3 levels in people with hyperthyroidism and euthyroid, but the differences between hypothyroid and euthyroid less clearly expressed.

Many factors unrelated to thyroid disease can cause abnormal T3 values.Therefore, total T3 values ​​should not be used alone in determining the thyroid status of the individual.In assessing the results of the analysis should take into account the content of serum T4, thyroxine binding globulin, TSH, and other clinical data.

Free T3

free triiodothyronine is 0.3% of the total blood triiodothyronine.However, it was he who provides the entire spectrum of metabolic activity, and implements negative feedback to the pituitary gland.CT3 is subdivided level does not depend on the concentration of TSH, it accurately describes the definition of thyroid status, regardless of fluctuations in the content of transport proteins.

thyroxine binding globulin

thyroxine binding globulin (TBG) - is a glycoprotein with a molecular weight of 54,000 dalton, consisting of a single polypeptide chain.It is one of three carrier proteins thyroid hormones such as thyroxine (T4) and 3,5,3'-triiodothyronine (T3);besides him to carrier proteins thyroid hormones are thyroxine-binding prealbumin (LSPA) and albumin.Although TSH is present in much smaller amounts than albumin and LSPA, it has a much higher affinity for the thyroid hormone and thus is the primary binding of the protein.In healthy individuals, only 0.05% of the total T4 present in serum is in a free (unbound) form.Bound distributed among T4 binding proteins as follows: TBG 70 - 75%, LSPA 15 - 20% albumin and 5 - 10%.

antibodies to thyroglobulin

Thyroglobulin - glycoprotein with a molecular weight of 660,000 Daltons, composed of two subunits, produced only by the thyroid gland.It is an essential component of thyroid colloid and is present in the serum of healthy individuals.Autoantibodies to thyroglobulin (Tg AT) using sensitive immunoassays are determined in low concentrations in the serum of 4 - 27% of healthy people;at higher concentrations, they are determined in 51% of patients with Graves' disease and 97% - with Hashimoto's thyroiditis and in 15 - 30% of patients with differentiated thyroid carcinoma.Measurements of antibodies to TG has long been used in conjunction with the determination of antibodies to thyroid peroxidase (AT to TPO), helping in the diagnosis of autoimmune thyroid diseases.It is likely that the analysis of AT to TPO as a major test for autoimmune diseases of the thyroid gland to replace a combination of antibodies to TG / AT to TPO due to the higher sensitivity of the test antibodies to TPO in Graves' disease and Hashimoto's thyroiditis.

useful to measure antibodies to TG in all sera to be tested for thyroglobulin.Since thyroglobulin autoantibodies can interfere in immunoassays based on competitive binding or immunometric assay at thyroglobulin, all patients must fulfill sensitive immunoassay for antibodies to thyroglobulin to eliminate their effect.thyroglobulin on results of the analysis in case of detection of antibodies in the patient to thyroglobulin should not be considered.

AT to TG measurements can also provide useful prognostic information in patients undergoing surgical treatment of differentiated thyroid carcinoma.If the patient had antibodies to TG, postoperative levels of antibodies to TG in the serum will remain constant or increase when persistence or progression of the tumor, whereas in patients admitted after a long observation practically cured, AT to TG levels generally decrease.

Antibodies to thyroid peroxidase

Antibodies to thyroid peroxidase autoantibodies are to this enzyme.The enzyme thyroid peroxidase will catalyze a process of iodination of tyrosine in thyroglobulin during the biosynthesis of T3 and T4.Until recently, these antibodies were named antimikrosomalnymi (AMA) since they bind to the microsomal part tireotsitov.Modern research has found that thyroid peroxidase is a major antigenic component of the microsomes.

Autoimmune thyroid disease is a major factor underlying hypothyroidism and hyperthyroidism and usually develop in genetically predisposed people.Thus, the measurement of circulating antithyroid antibodies is a marker for genetic predisposition.The presence of antibodies to TPO and elevated TSH levels can be predictive of the development of hypothyroidism in the future.

main autoimmune thyroid diseases are Hashimoto's thyroiditis and Graves' disease.In virtually all cases, Hashimoto's disease and Graves' disease most cases raised antibodies to TPO.High levels of antibodies to TPO in combination with clinical manifestations of hypothyroidism, confirms the diagnosis of Hashimoto's disease.

Thyroglobulin Thyroglobulin

- glycoprotein with a molecular weight of 660,000 Daltons, composed of two subunits, produced only by the thyroid gland.It is an essential component of thyroid colloid and is present in the serum of healthy individuals.TG is used as a marker of tumors in the thyroid gland, and in patients with thyroid removed or have been subjected to radioactive iodine therapy, - to evaluate the effectiveness of the treatment.

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