[Clinical significance of thyrotropin measurement by immunoradiometric assay and thyrotropin-releasing hormone test].

The levels of serum TSH were measured by a sensitive immunoradiometric assay (IRMA) method and the responses of TSH to TRH stimulation were observed in three groups of hyperthyroidism, primary hypothyroidism and secondary hypothyroidism. The levels of serum TSH were found to be undetected in 98% (1/51) of the patients with hyperthyroidism, very high in 100% (35/35) of the patients with primary hypothyroidism and normal in 91% (30/33) of the patients with secondary hypothyroidism. TRH test showed no responses of TSH in all patients with hyperthyroidism, high responses in all patients with primary hypothyroidism and blunt responses in 69% (11/16) of patients with secondary hypothyroidism. The results indicate that the measurement of serum TSH by IRMA is a sensitive index in the diagnosis of hyperthyroidism and primary hypothyroidism, but can not be differentiated the secondary hypothyroidism from normal conditions. TRH test may be helpful in the differential diagnosis between secondary hypothyroidism and normal conditions.