Thyroid stimulating hormone (TTH, TSH)
Why this test?
Help diagnose thyroid disorders and monitor the treatment of hypothyroidism and hyperthyroidism; sometimes the TSH test is used to screen newborns for congenital hypothyroidism
In what cases is it prescribed?
- If you have signs and symptoms of hyperthyroidism or hypothyroidism and/or an enlarged thyroid gland (goiter), or if you have a thyroid nodule or nodules;
- when you already have thyroid problems and receiving treatment
Thyroid-stimulating hormone (TSH) is produced by the anterior lobe of the pituitary gland. In the body, TSH controls the processes of metabolism, growth and development of the body. In particular, TSH regulates the synthesis of thyroid hormones: T4 - thyroxine and T3 - triiodothyronine, where the concentration of TSH directly depends on the amount of these substances in the blood. The main clinical significance of TSH analysis is the assessment of thyroid gland function. But, since it interacts very actively with hormones, it is important to see the ratio of TSH, T3 and T4 for decoding. The norm of TSH differs depending on a person's gender and age. In addition, the norm is affected by low-calorie nutrition and the period of pregnancy.
TSH (thyreotropic hormone, thyrotropin, Thyroid-stimulating Hormone, TSH, Thyrotropin) is one of several glycoprotein hormones of the pituitary gland (LH, FSH, TSH), which consist of two non-covalently linked peptide chains: an α-chain, similar in structure for all these hormones, as well as the β-chain responsible for biological and immunological specificity. TSH, which is produced by the anterior lobe of the pituitary gland, is the main regulator of thyroid function.
Thyrotropin-releasing factor (TRF) of the hypothalamus controls the level of TSH secretion, which, in turn, regulates the secretion of the thyroid hormones triiodothyronine (T3) and thyroxine (T4). There is a negative feedback mechanism controlled by the hypothalamus, which is sensitive to the concentrations of thyroid hormones T3 and T4 circulating in the bloodstream.
This entire complex belongs to the so-called hypothalamic-pituitary-thyroid system. Possible changes in the function of this system can affect the concentration of T3 and T4 in the blood. TSH affects the main metabolic processes in the thyroid gland, binding to the cell membrane receptor and activating adenylate cyclase. In turn, adenylate cyclase triggers the production of cyclic AMP - the «second messenger» of TSH, which provides a cascade of metabolic reactions in the cell. Due to this activation, the synthesis and secretion of T3 and T4 is enhanced, as well as the physical and functional integrity of the thyroid gland is supported.
The main clinical value of determining the concentration of TSH in the blood (TSH analysis) is to assess the function of the thyroid gland. Analysis of the hormone TSH allows you to determine the concentration of TSH in the blood. TSH analysis is recommended in the following cases: - in order to exclude hyperthyroidism (reduced or undetermined TSH level) or hypothyroidism (increased TSH level) - to monitor antithyroid therapy in hyperthyroidism or T4 replacement therapy in primary hypothyroidism - to control the suppression of T4 - the trophic effect of TSH in «cold nodes» and non-toxic goiter - to evaluate the response to the stimulation test - thyrotropin-releasing factor (TRF) Since accurate and sensitive methods for the determination of thyroid-stimulating hormone are now available, TSH analysis is used to diagnose latent and subclinical forms of hypothyroidism or hyperthyroidism.