Thyroid Stimulating Hormone (TSH) ELISA
A solid phase enzyme immunoassay for the quantitative determination of TSH in blood serum or plasma.
Thyroid stimulating hormone (TSH) is a glycoprotein with molecular weightca.30 KD which is secreted by hypophysis. A molecule of TSH consists of two none covalently bound sub units: α-and β-HCG. β-subunit determines biological activity and immunological specificity of TSH.
TSH stimulates thyroid gland to secrete thyroid hormones. TSH secretion in hypophysis is controlled by a negative feedback regulation by thyroid hormones.TSH secretion is subject to circadian rhythms with highest levels seen early in the morning (6a.m.).Changes of TSH blood level during a day are not significant; never the less, if the results do not correspond with clinical status and other laboratory data, it is recommended to take and test another blood sample. Determination of TSH level in serum is recommended in the following states and conditions:
- Diagnostics of dysfunction of the thyroid gland;
- Hypothyroidism (TSH level is increased. The diagnosis is confirmed by low concentrations of total and freeT4 andT3.In mild subclinical forms whenT4 and T3 levels are within normal ranges, determination of TSH concentration is critical);
- Hyperthyroidism(synthesis and secretion of TSH are inhibited);monitoring of replacement therapy;
- Screening for inherited hypothyroidism (on day 5 after birth TSH level in blood is determined).TSH level is elevated just after birth but it comes within the normal range in several days (both in boys and in girls). Serum TSH level is elevated during pregnancy, after physical stress, in individuals with lowered blood pressure and lowered temperature. Secretion of TSH is inhibited by Cortical and Growth hormone .Low TSH levels are often seen in elderly people, in patients with chronicrenalin sufficiency, liver cirrhosis, in retardation of sexual development, in secondary amenorrhea, Cushing syndrome, acromegaly.
In a present test system-chain specific monoclonal antibodyXTB78 is used as capture reagent; enzyme-labeled (Fab2)-fragment of another β-chain specific monoclonal antibodyXTB11 is used as tracer. This combination enables to minimize both cross-reactive reactions with other pituitary hormones and false positivity caused by anti-species antibodies.
The Wel-Lisa TSH test is based on sandwich enzyme immunoassay principle. Tested specimen is placed into the microwells coated by specific murine monoclonal to β chain human TSH-antibodies. Antigen from the specimen is captured by the antibodies coated microwell surface. Second antibodies murine monocnoclonal to (Fab2) fragment of β chain human TSH, labeled with peroxidase enzyme, are added in the microwells. After washing procedure, the remaining
enzymatic activity bound to the microwell surface is detected and quantified by addition of chromogen-substrate mixture, stop solution and photometry at 450 nm. Optical density in the microwell is directly related to the quantity of the measured analyte in the specimen.
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