Thyrotroph function assessed by sensitive measurement of thyrotropin with three immunoradiometric assay kits: analytical evaluation and comparison with the thyroliberin stimulation test.

Abstract

We evaluated the analytical and clinical performance of three "sensitive" immunoradiometric assay (IRMA) kits (Tandem-R TSH HS, Hybritech, Inc.; EchoClonal TSH, Bio-Rad; Coat-A-Count TSH IRMA, Diagnostic Products Corp.) for measurement of thyrotropin (TSH) and compared their performance against a "regular" IRMA (ARIA-HT, Becton-Dickinson) to determine whether these assays might eliminate the need to perform the thyroliberin (TRF) stimulation test. We concluded that the Tandem and EchoClonal kits may obviate the need to perform TRF stimulation tests in some patients. Using only the basal TSH concentration to predict the TSH response to TRF, we found all three sensitive TSH assays to be useful for detecting abnormal thyrotroph function. Dose-response, linearity, analytical recovery, and specificity were acceptable for all kits, but intra-assay precision at very low TSH concentrations and analytical sensitivity differed considerably among the kits. Using the EchoClonal assay, we established a normal reference interval for TSH of 0.4-4.6 milli-int. units/L.

Prevalence of thyroid dysfunction in patients with acute atrial fibrillation attended at a cardiology emergency room

“…4,5 This large variation may arise from different ages of subjects evaluated, 6,7 different regions where the studies were carried out, 8 presence of associated illness and use of medications 9 and different methods of measuring thyroid hormones and thyroidstimulating hormone. 10,11 The development of thyroid-stimulating hormone assays with improved sensitivity has changed the diagnosis of thyroid dysfunction. Subclinical hypo and hyperthyroidism are being diagnosed by the presence of high and low thyroid-stimulating hormone, respectively, in association with normal free thyroid hormone values in asymptomatic individuals.…”