A sensitive technique for determination of thyroid-stimulating immunoglobulin (TSI) in unfractionated serum.

A new sensitive and reproducible technique for the determination of thyroid stimulating immunoglobulins is described. This procedure employs cells obtained from primary culture of human thyroid gland. We measured the increase of cyclic AMP after addition of patient sera. The major advantages of this procedure are the improved sampling throughout with the ability to measure eighty samples simultaneously without fractionation of serum. This large sample allows us to test forty sera together and to assay in duplicate, thus increasing the validity of the results. The TSI activity is associated with the immunoglobulins G (IgG) fraction and we obtained a linear dose response curve with IgG as well as with whole serum. The results obtained in various thyroid diseases are discussed.