The serum TSH of 452 patients were measured with a two-site immunoradio-metric assay （IRMA）. The serum TSH level was 1.69±0.95μIU/ml in euthyroid subjects

and was much lower in patients with hyperthyroidism （i. e. 0.3μIU/ml） which returned to nearly normal in 85% patients who were in remission stage. On the contrary

serum TSH level elavated to more than 5μIU/ml in patients with hypothyroidism. TRH stimulation test showed that the baseline serum TSH values correlated well with the peak serum TSH value post-TRH （r=0.88）. TSH （IRMA） improved the sensitivity over that of conventional radioimmunoassays

hence has made possible discrimination between hyperthyroid

euthyroid and hypothyroid subjects

and may serve as a first-line test in the diagnosis of thyroid dysfunction. In addition

when serum thyroid hormone levels have been brought to normal range

a further "fine adjustment" of treatment based on serum TSH levels appears to be helpful to achieve physiologically and biochemically.