TSH / REF: HYE-5385

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.