The use of proteolytic enzyme inhibitor (Trasylol) in radioreceptor assay of TSH-its application to measuring thyroid stimulating immunoglobulins (TSI) in thyroid diseases.

In order to estimate thyroid stimulating immunoglobulins (TSI) in serum, a stable, reproducible and sensitive radioreceptor assay (RRA) capable of detecting 100 micromicron of thyroid stimulating hormone (TSH) has been developed using a proteolytic enzyme inhibitor (Trasylol), partially purified human TSH and particulate fractions of human thyroid homogenate. The binding of 125-I-labelled TSH to the crude thyroid membranes was significantly increased from 2-3% to 15-20% in the presence of Trasylol (2000 KIU per tube). Further investigations suggested that Trasylol might inhibit the aggregation of 125I-labelled TSH during incubation with these membranes. With this assay system, the serum immunoglobulins from a great majority of untreated patients with Graves' disease were shown to inhibit the binding of 125I-labelled TSH to those membranes more markedly than those from control subjects. Therefore, this RRA for TSH was considered to provide a sensitive and stable method for detecting TSI.