Autoimmune thyroid diseases: In vitro diagnostics

Abstract

In diagnostics of autoimmune thyroid diseases a number of in vitro methods is used to evaluate thyroid function or examine the presence of an tithyroid antibodies which may be included in pathogenesis of the disease or only represent "silent witnesses" of autoimmune processes. During the evaluation of thyroid function serum concentrations of thyroid-stimulating hormone (TSH) and thyroid hormones are determined and due to these concentrations the diagnosis of manifested or subclinical disturbances of thyroid gland is set. Detection of antibodies specific in dominant thyroid auto antigenes represents confirmation of autoimmune pathogenesis of the disease. The concentration of TSH and thyroid hormones in blood may be influenced by some diseases and drugs, so abnormal values can be detected in absence of diseases of thyroid gland. In the serum of a tested person heterophilic antibodies, rheumatoid factors or other antibodies may occur which reduce the number of specific interactions in the assay, causing increased or decreased concentrations of hormones or autoantibodies. A great number of methods used in in vitro diagnostics differs very much by sensitivity which should be considered during the interpretation of laboratory results. This study presents the most important methods used in diagnostics of autoimmune thyroid diseases.

U dijagnostici autoimunskih bolesti štitaste žlezde koriste se brojne in vitro metode kojima se procenjuje tireoidna funkcija ili ispituje prisustvo antitireoidnih autoantitela koja mogu biti uključena u patogenezu bolesti ili samo predstavljati "neme svedoke" autoimunskog procesa. Pri proceni funkcije štitaste žlezde određuju se serumske koncentracije tireostimulišućeg (TSH) i tireoidnih hormona i na osnovu njihove koncentracije postavlja dijagnoza ispoljenih ili subkliničkih poremećajafunkcije štitaste žlezde (hipertireoze ili hipotireoze). Potvrdu autoimunske patogeneze bolesti predstavlja detekcija antitela specifičnih za dominantne tireoidne autoantigene (receptor za TSH, tireoidnu peroksida zuitireoglobulin). Na koncentraciju TSH i tireoidnih hormona u krvi mogu uticati neka fiziološka stanja, bolesti i lekovi, tako da se abnormalne vrednosti mogu detektovati i u odsustvu bolesti štitaste žlezde. U serumu ispitanika mogu biti prisutna heterofilna anti tela, reumatoidni faktori ili druga auto anti tela koja smanjuju broj specifičnih interakcija u testu prouzrokujući povećanu ili smanjenu koncentraciju hormona ili autoantitela. Veliki broj metoda koje se koriste u in vitro dijagnostici veoma se razlikuju prema osetljivosti, što treba imati u vidu prilikom interpretacije laboratorijskih rezultata. U ovom radu su prikazane najvažnije metode koje se koriste u dijagnostici autoimunskih bolesti štitaste žlezde: Graves-ove bolesti i Hashimoto tireoiditisa.