Clinical application of a cytochemical bioassay for the determination of thyroid stimulating hormone

Thyroid stimulating hormone (TSH) was measured using a highly sensitive cytochemical bioassay (CBA) technique in normal subjects, in patients with Graves' disease (untreated and treated) and in patients with euthyroid goiter and negative thyrotropin-releasing hormone (TRH)-test. Plasma TSH levels of normal subjects and of subjects with untreated Graves' disease were reduced after the plasma had been incubated with a specific antibody to human TSH, indicating that the thyroid stimulating substance measured with this assay was likely to be TSH. Basal TSH levels in patients with Graves' disease and in a special group of patients with euthyroid goiter and negative TRH test were low but detectable. They did not rise after TRH administration. Increased TSH release (4.5- to 10-fold) after TRH stimulation was demonstrated, however, in two formerly hyperthyroid patients after treatment. This increase was not detected by radioimmunoassay (RIA) due to limited sensitivity.