SERUM THYROTROPIN AND CIRCULATING THYROGLOBULIN AND THYROID MICROSOMAL ANTIBODIES IN A FINNISH POPULATION

Circulating thyroglobulin antibodies (TgA) were detected in 7.9% and thyroid microsomal antibodies (MsA) in 25.8% of a sample of 507 subjects in the adult population of southern Finland when titres as low as 1/5 for TgA and 1/10 for MsA were included. Both antibodies were measured by passive haemagglutination techniques. The prevalence of high titres was 0.6% for TgA (≥ 1/25 000) and 4.2% for MsA (≥ 1/100 000). Eighty-eight per cent of the TgA positive subjects also had MsA. The MsA titres were usually markedly higher than those of TgA in the same subjects. Serum thyrotrophin (TSH), cholesterol and triglycerides were measured in 123 euthyroid subjects with thyroid antibodies and no history of thyroid diseases, and in controls matched for age and sex. Serum TSH was elevated in 31% of the TgA positive subjects and the mean TSH concentration was significantly above that of the controls. All 3 subjects with high TgA titres also had elevated TSH levels. Serum TSH concentration was increased also in 25% of those with MsA and the mean TSH value was significantly above the control level. High MsA titres were found in 19 subjects and the serum TSH was elevated in 10 of them (53%). The prevalence of symptomless autoimmune thyroiditis (SAT) was 2 and 5%, of the population when high titres of either TgA or MsA, respectively, and elevation of serum TSH was used as criteria. This fits with our previous observations. There was no difference in serum cholesterol or triglycerides in the TgA or MsA positive subjects or in the corresponding matched controls.