Bioassay and Immunoassay Measurements of Serum Thyrotropin in Primary Hypothyroidism Before and After the Administration of Thyrotropin Releasing Hormone[*]

Abstract

After the administration of synthetic thyrotropin releasing hormone (TRH) to 4 patients with primary hypothyroidism, elevation of serum thyrotropin (TSH) level was demonstrated when measured by bioassay as well as radioimmunoassay for TSH. The time response curves in McKenzie's bioassay using these sera were normal TSH type. In McKenzie's bioassay as well as radioimmunoassay, multiple dilutions of sera obtained after TRH administration resulted in dose response curves which was parallel to that obtained for sera before TRH. The ratio of bioassay and immunoassay potency estimates for TSH in sera obtained before TRH was 2.9 ± 0.19 (mean ± one standard deviation) which was not statistically different from the ratio obtained after TRH (2.5 ± 0.69). Hence these findings suggest that TSH induced by TRH seems to be identical with TSH increased by negative feedback mechanism.

Thyrotropin - Radioimmunoassay - Bioassay - Thyrotropin Releasing Hormone

1 Presented in part, at the 19th Annual Meeting of Western Branch of Japan Endocrinological Society, Kobe, October 27, 1971.