Recombinant human TSH (rec-hTSH; Thyrogen, lot M-17073) obtained from transformed Chinese hamster ovary cells was tested for both radioiodination and preparation of a secondary standard used in RIA and immunoradiometric assay (IRMA) for routine clinical investigation. Results were compared to those obtained with high quality pituitary TSH (pit-hTSH; Dr. P. Torjesen, Oslo, Norway; and NIDDK, Rockville, MD), traditionally used in these assays. After extensive characterization and testing, it was found that [125I]rec- hTSH matched all binding and chromatographic criteria usually obtained with [125I]pit-hTSH, including Stokes' radius, labeling, and storage stability, and did not introduce any significant bias when used in the measurement of unknown serum samples. A preparation of rec-hTSH was calibrated against a local secondary standard as well as against two well known international reference preparations (NIDDK hTSH RP-1 and WHO International Reference Preparation 80/558) by IRMA and RIA. In the RIA, NIDDK anti-hTSH-3 polyclonal antibody was used, whereas in the IRMA, two commercial preparations were used: a monoclonal antibody as the detecting antibody, and a polyclonal antibody as the capture antibody. In both assays, the recombinant standard preparation yielded good fit displacement curves, showing significant parallelism compared to pit-hTSH and therefore allowing an unbiased measurement of unknown serum samples. The specific activity of the rec-hTSH preparation calibrated against the WHO International Reference Preparation was 7.7 IU/mg protein when measured by IRMA and 7.1 IU/mg when measured by RIA. In conclusion, these results indicate for the first time that rec-hTSH can fully replace pit-hTSH as both standard and tracer in diagnostic in vitro systems such as RIA and IRMA, suggesting that other recombinant glycosylated hormones might also serve for immunoassay reagent preparation.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Clinical Biochemistry
- Biochemistry, medical