Serum Thyrotrophin and Circulating Thyroglobulin Antibodies in Subjects With Non-Toxic Goitre and in Euthyroid Subjects Who Had Undergone Subtotal Thyroidectomy or Radioiodine Therapy

As part of a multiphasic health examination in two regions in the east of Finland, 5492 adult subjects were studied in the province of Kainuu and 2767 in the city of Joensuu. The general prevalence of goitre was 6.0 % in the Kainuu region and 4.2 % in Joensuu and that of frank hypothyroidism 0.3 and 0.4 %, respectively. The serum thyrotrophin (TSH) and circulating thyroglobulin antibodies (TgA) were determined in subjects with non-toxic goitre, in euthyroid subjects who had undergone thyroidectomy or radioiodine therapy, and in matched controls without thyroid disease. In a group of 99 subjects with non-toxic goitre the mean serum TSH (2.9 μU/ml) did not differ from the mean (2.9 μU/ml) of the 40 corresponding controls. Of the 36 subjects who were euthyroid after thyroidectomy without recurrent goitre, 9 had an elevated serum TSH level, and the mean value for this group (5.8 μU/ml) was significantly higher than the mean (3.5 μU/ml) for the 36 controls. Of the 19 subjects with recurrent non-toxic goitre, 2 had an elevated serum TSH level, but the mean value (5.0 μU/ml) was not significantly higher than the mean (3.4 μU/ml) for the 19 controls. Of the 15 subjects who were euthyroid after radioiodine therapy, 4 had an elevated serum TSH level, and the mean value (6.2 μU/ml) was significantly higher than the mean of the 15 controls (3.3 μU/ml). The subjects with non-toxic goitre and positive TgA titres had a significantly higher mean serum TSH than those with goitre but negative TgA titres (3.8 against 2.7 μU/ml). The thyroidectomized subjects without recurrent goitre who had detectable TgA had a significantly lower mean serum TSH than the corresponding subjects who were TgA-negative (4.0 against 6.4 μU/ml). The subjects with recurrent goitre and positive TgA titres had a higher mean TSH level than those without TgA (7.6 against 3.5 μU/ml). but the difference was not significant. Subjects previously treated with radioiodine who had positive TgA titres had a lower mean serum TSH than those who were TgA-negative (4.6 against 6.8 μU/ml), but the difference was not significant. About a fourth of the subjects who were euthyroid after previous thyroidectomy or radioiodine therapy in the present study had elevated serum TSH values, indicating slight thyroid failure. The present results also indicate that auto-immune phenomena may play some part in producing slight thyroid failure in non-toxic goitre, but that other factors are responsible for the elevated TSH values in euthyroid subjects after thyroidectomy or treatment with radioiodine.