Antibodies to the thyroid gland and to the thyrotrophin receptor in African and Indian thyrotoxic patients.

Sixty two thyrotoxic patients, 34 African and 28 Indian, were studied in order to assess the prevalence of thyroid antibodies and TSH binding inhibitory activity (TBI): 45 had Graves' disease and 17 had toxic nodular goitres. Microsomal and thyroglobulin antibodies were positive more often in Indian than in African patients with Graves' disease (microsomal 52% vs 37.4%, P less than 0.05; thyroglobulin 38.1% vs 4.2%, P less than 0.001). Patients with toxic nodular goitres had a lower prevalence of positive microsomal antibodies (P less than 0.01), but not of thyroglobulin antibodies (P = 0.1) when compared with patients with Graves' disease. TBI activity measured by a radioreceptor assay was positive in 43 of the 45 (95%) patients with Graves' disease and only 1 of the 17 patients (5.9%) with toxic nodular goitre. It thus appears that TBI activity is a sensitive marker in the diagnosis of Graves' disease and that there is a lower prevalence of thyroglobulin and microsomal antibodies in African patients compared with Indian patients.