Determination of Plasma Thyroid Hormones by Chemiluminescence and Radioimmunoassay Methods in Calves

The various methods for determination of the plasma thyroid hormones concentrations have been studied in some species and selection of a proper method is necessary for accurate determination of these hormone levels. The aim of this study was to evaluate the plasma thyroid hormones concentrations by both chemiluminescence (CLIA) and Radioimmunoassay (RIA) methods in calves. Blood samples were collected from the jugular vein of 30 clinically healthy animals, aged 1-6 months and of different sexes during summer. The plasma was analyzed to determine thyroxine (T4) and triiodothyronine (T3) concentrations. According to the results, there was a significant difference in the T4 (P < 0.0001) and T3 (P < 0.05) concentrations between two methods and that levels of these hormones were higher in RIA method. The linear regression analysis of both hormones showed that the RIA and CLIA results was significantly correlated (T4: P < 0.01, r = 0.677; T3: P < 0.05, r = 0.538). Additionally, we observed a significant difference between two sexes concerning the thyroid hormones in both methods, except to the T3 when using the CLIA method. In conclusion, determination of the T4 and T3 concentrations using the RIA method had an acceptable limit of sensivity and precision; also it was more appropriate than the CLIA method for research application in calves.