THE RELATIONSHIPS BETWEEN SERUM T3 INDEX, THYROID VOLUME, AND THYROID STIMULATING, TSH RECEPTOR BINDING AND THYROID GROWTH STIMULATING ANTIBODIES IN UNTREATED GRAVES' DISEASE

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Abstract
SUMMARY: This study represents an international double‐blind collaborative study of abnormal immunoglobulin activity in untreated Graves' disease. Laboratories in two countries participated in a comparison of thyrotrophin binding inhibiting (TBII), thyroid stimulating (TSAb), and growth stimulating (TGI) immunoglobulins with clinical data, including ultrasonically measured thyroid size. The correlation between TGI and thyroid volume (n= 25, Rs= 0.54, P < 0‐05) and the fact that 9 of 10 patients with high range TGI values had large goitres establish the relationship between TGI and goitre, confirming that the in‐vitro activity of these antibodies is related to an in‐vivo action. In addition, both TBII and TSAb correlated with serum free T3 indices (TBII: n= 60, Rs= 0.46, P < 0.001, and TSAb: n= 60, Rs= 0.64, Pn= 60, Rs= 0.37, P< 0.01, and TSAb: n= 60, Rs= 0.41, P < 0001) suggesting that these antibodies are also important in development of goitre in Graves' disease. Finally, some correlation between the antibodies was observed. TBII correlated with TSAb (n= 60, Rs= 0.47, P < 0.001), and in the 16 patients with positive TGI results, this activity correlated with TBII (Rs= 0.54, P <0.05), but not with TSAb. Also some cases were found with corresponding high range TBII and TGI, while negative for TSAb, suggesting a close relationship between the in‐vitro measurement of TSH binding and TGI.