Description
The DRG:HYBRiD-XL TSH is an enzyme immunoassay for the quantitative in vitro diagnostic measurement of thyroid-stimulating hormone (TSH) in serum and heparin plasma.
Only for use with the DRG:HYBRiD-XL Analyzer.
Thyroid-stimulating hormone (TSH) also known as thyrotropin, is a glycoprotein hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland. TSH stimulates the thyroid gland to produce thyroxine (T4), and then triiodothyronine (T3) which stimulates the metabolism of almost every tissue in the body (1).TSH release from the pituitary is regulated by thyrotropin releasing hormone (TRH), which is secreted by the hypothalamus, and by negative feedback of T4 and T3 at the pituitary and hypothalamus. Increased levels of T3 and T4 reduce the response of the pituitary to the stimulatory effects of TRH (2). Measurement of TSH is the first line diagnosis of thyroid dysfunction.
If TSH is out of its reference range, determination of free T4 becomes important for differential diagnosis (3). In most cases TSH and free T4 show inverse correlation. Increased concentration of TSH in conjunction with decreased free T4 concentration indicate primary hypothyroidism while low TSH in combination with high free T4 confirms primary hyperthyroidism. In addition, TSH neonatal screening is established in many countries as routine control to detect congenital hypothyroidism, characterized by very high TSH and low free T4 concentrations which can cause mental retardation if left untreated (4). Under conditions of pituitary TSH deficiency (secondary hypothyroidism) or insufficiency of stimulation of the pituitary by TRH (tertiary hypothyroidism), concentrations of free T4 are usually low and TSH levels are generally low or normal. The TRH stimulation test differentiates these conditions. This method is a second-generation assay, which provides the means for discrimination in the hyperthyroid-euthyroid range.
The DRG:HYBRiD-XL TSH Kit is a solid phase enzyme-linked immunosorbent assay (ELISA) based on the sandwich principle. The antibody coated wells (ACW) of the reagent cartridges are coated with a monoclonal [mouse] antibody directed towards a unique antigenic site of the TSH molecule. An aliquot of patient sample containing endogenous TSH is incubated in the coated well with enzyme conjugate, which is an anti-TSH antibody conjugated with horseradish peroxidase. After incubation the unbound conjugate is washed off.
The amount of bound peroxidase conjugate is proportional to the concentration of TSH in the sample. Having added the substrate solution, the intensity of colour developed is proportional to the concentration of TSH in the patient sample.
