Thyroid stimulating hormone receptor antibody in thyroid diseases

Thyroid stimulating hormone receptor antibody (TRA) was estimated as a measure of TSH binding inhibitory immunoglobulin (TBII) in 48 persons. These included (i) 14 controls; (ii) 23 patients with Graves' disease who were tested for TRA within 3 months of commencing treatment with carbimazole of which 13 were studied serially; (iii) 5 patients with toxic nodular goitre; (iv) 4 with euthyroid exophthalmos; and (v) 2 neonates of thyrotoxic mothers. TRA was measured with an RIA system, while total thyroxine (T4), free thyroxine concentration (FTC) and TSH were also estimated along with TRA. All controls showed undetectable TRA levels; 87 per cent of patients with Graves' disease were TRA positive within 3 months of starting carbimazole therapy. In the serial study, 5 patients with Graves' disease who had undetectable TRA initially remained so while on treatment. Seven out of the remaining 8 patients showed a decline of TRA levels to normal over 3 to 18 months. This decline coincided with clinical and biochemical recovery.