Thyrotropin receptor antibodies in black South African patients with Graves' disease and their response to medical therapy

Graves' disease is increasing in incidence amongst urban black South Africa ns. The pathogenic role of thyrotropin receptor antibodies (TRAb), crucial in other populations, has not been formally evaluated in African communitie s. We therefore prospectively investigated the prevalence of TRAb in 30 con secutive urban black South African patients with classical Graves' disease at the onset of their illness. This was compared with the frequency of thyr oid microsomal and thyroglobulin antibodies in the same patients. Ten patie nts with euthyroid goitres unrelated to Graves' disease and 10 healthy cont rols were also studied. Twenty of the hyperthyroid patients were retested 4 -6 months after starting carbimazole therapy and ten of them again after 1 year. initially 83% of patients were positive for TRAb as against 54% for t hyroid microsomal and 17% for thyroglobulin antibodies. After 4-6 months of treatment, 65% of patients still had elevated (>15% inhibition of binding) TRAb titres, while at 1 year this had dropped to 40% (4 out of 10 patients ). All positive patients had relapsed biochemically, while TRAb negative pa tients were all in remission. We conclude that TRAb are a sensitive and spe cific marker of Graves' disease in black South Africans and closely paralle ls the response to medical therapy at 1 year. However, their predictive val ue for delayed relapse requires the study of a larger cohort of patients ov er a longer time-frame. (C)1998, Editrice Kurtis.