Pathophysiological and clinical implications of thyroid growth-stimulating immunoglobulins: evidence for their intrathyroidal production.

Thyroid growth-stimulating immunoglobulins are responsible for goitre formation not only in Graves' and Hashimoto's disease but also (partly) in simple goitre, especially in recurrent cases. TGI are antibodies, the TSH receptor, however, appears not to be the antigenic site in simple goitre. In our own studies two TGI assay systems ([3H]thymidine incorporation into isolated porcine thyroid follicles and into FRTL-5 cells) gave comparable results. TGI was found in 20 out of 72 patients with simple goitre (27%) coming from an endemic goitre area (biased by selection, i.e. certainly including sporadic forms) and in 10 out of 26 patients (38%) with recurrent goitre. TGI levels were higher in thyroidal venous blood compared to cubital blood (simultaneously drawn during surgery) indicating an intrathyroidal production of TGI. Thyroid growth-blocking antibodies as estimated in the FRTL-5 cell assay in one of our patients might be of significance not only in primary myxoedema but also for congenital hypothyroidism.