[Clinical evaluation of routinely applied highly sensitive TSH-RIA]

Forty-one routine TSH assays were carried out by applying newly developed, highly sensitive TSH RIA (T. Mori, et al., Folia Endocrinol. Jap., 56: 1231, 1980). B/B0 percent of the least standard point (0.156 microU/ml) was consistently lower than B0 and higher than that of 0.31 microU/ml. The distributions of assayed TSH concentrations in 1394 sera revealed that 34.8% of the total were in an undetectable range when measured by conventional method (less than 1.0 microU/ml), but this method picked up 16.4% (0.156-1.0 microU/ml), and only 5.4% exceeded the upper limit (20 microU/ml). TRH test results (500 micrograms i.v. bolus) in 45 cases of thyroid disorders with low or normal basal TSH revealed that the peak TSH of those with basal TSH of 0.156-1.0 microU/ml (8.98 +/- 4.15 microU/ml) was significantly different from those of less than 0.156 microU/ml or 1.0-3.2 microU/ml. Further, TSH concentrations in 19 patients after T3 administration (75 micrograms X 7 days) were 0.183 +/- 0.073 microU/ml, and all but one (0.43 microU/ml) showed values lower than the normal range (0.31-3.2 microU/ml). Thyroid hormone concentrations in cases with TSH of 0.156-1.0 microU/ml were limited in the ranges of less than 300 ng/dl T3 and/or less than 15 micrograms/dl T4, and these were considered to be the threshold of definite TSH inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)