Thyroid stimulating hormone in the blood serum

Reference values ​​of serum TSH concentration: newborns - 1-39 mIU / l, adults - 0.4-4.2 mIU / l.

TTG is a glycoprotein secreted by the adenohypophysis. Acts mainly on the thyroid gland, stimulating the synthesis of T4 and T3 and their release into the blood.

To determine the serum TSH level, RIA, ELISA and immunofemiluminescent analysis are used. The latter method is based on the use of monoclonal antibodies to TSH and enhancement of chemiluminescence, its sensitivity is two orders of magnitude greater than the sensitivity of RIA and one order of magnitude - ELISA.Modern diagnostic kits of the third generation allow detecting TSH concentrations of less than 0.01 mIU / l, so they can clearly distinguish between hyper-thyroidism( TSH content is reduced) and euthyroidism( normal TSH content).It is with the definition of the level of TSH that diagnostics should be started if suspicion of abnormalities in thyroid hormone activity is suspected.

With hypothyroidism, the concentration of TSH is increased. The diagnosis is confirmed by low concentrations of free thyroxine( cT4), T4, T3 in the blood. In cases of subclinical mild hypothyroidism, when the level of cT4 and T4 in the blood is within normal limits, the detection of elevated TSH content becomes crucial. A low level of TSH in hypothyroidism indicates a deficiency of the pituitary or hypothalamus and excludes primary dysfunction of the thyroid gland. The definition of TSH is important for monitoring patients with hypothyroidism who receive daily substitution therapy with levothyroxine sodium. Determining the concentration of TSH, you can optimize the dose of the drug.

In hyperthyroidism, the synthesis and secretion of TSH are suppressed. As a result, primary hyperthyroidism( thyroid disease) is characterized by an elevated content of thyroid hormones( T4, T3) in the blood and a deficiency of TSH.

The concentration of TSH increases with thyrotropine-secreting tumors of the pituitary gland( in 90% of cases, macroadenomas, more than 10 mm in size).At the same time, it must be remembered that long-term hypothyroidism can lead to pituitary hyperplasia with the formation of a pseudotumor, therefore, all patients need to examine the concentration of cT4 before performing an operation on the pituitary gland. Elevated values ​​of cT4 testify in favor of pituitary adenoma, low values ​​of hypothyroidism.

The main diseases and conditions in which the most frequent changes in the concentration of TSH in the blood are presented in the table.

Table Diseases and conditions in which the concentration of serum TSH is changed