Clinical application of a sensitive non-isotopic immunometric assay of thyrotropin.

We have evaluated an immunometric assay of thyrotropin (TSH) based on enhanced chemiluminescence signal; its detection limit is 0.06 milli-int. unit/L. Values in 101 clinically euthyroid subjects with normal thyroid hormone concentrations ranged from 0.39 to 6.83 milli-int. units/L. TSH in 15 hypothyroid patients ranged from 10.3 to greater than 200 milli-int. units/L, whereas in 31 hyperthyroid subjects with increased concentrations of free thyroxin and free triiodothyronine, TSH was undetectable serum of all but one subject. Of 32 clinically and biochemically euthyroid patients with goiter, two had undetectable serum TSH and six had values below the normal range. In 19 clinically euthyroid patients from an intensive-care unit, TSH was undetectable in two and below the normal range in another two. This immunometric chemiluminescence assay distinguishes thyrotoxic from euthyroid subjects, but caution is required in interpreting TSH values alone in subjects with goiter or nonthyroidal illness.