Thyroid disease and high concentration of serum thyrotrophin in a population sample of women. A 4-year follow-up.

In a population study in Göteborg, Sweden, comprising women in the age strata 44, 52, 56, 60 and 66 years, serum thyrotrophin (S-TSH) was determined in 283 women representative of the general population of women of these ages. No women with previously unknown hypothyroidism were found at the clinical examination; 47 (3.7%) were on thyroxine treatment, 9 (0.7%) because of spontaneous hypothyroidism. Sixteen women (1.2%) had markedly elevated S-TSH concentration (less than 14 mU/l). They were studied further by determination of thyroid hormones and circulating antithyroid microsomal and thyroglobulin antibodies, and those with goiter were subjected to fine-needle biopsy of the thyroid gland. They were furthermore followed for four years. Four euthyroid women were given thyroxine because of goiter and abnormal laboratory test results. Of nine individuals with high S-TSH concentration as well as high titers of thyroid antibodies and/or biopsy evidence of autoimmune thyroiditis, seven became hypothyroid within the four years of follow-up. The other two women had consistently elevated basal S-TSH concentration and exaggerated S-TSH response after thyroliberin administration. We conclude that the majority of individuals without previously recognized thyroid disease who have S-TSH concentration above 14 mU/l with the assay used will require thyroxine therapy within a few years. In one woman, however, with multinodular colloid goiter and high titer of antimicrosomal antibodies, the basal S-TSH concentration decreased during follow-up to a high normal value; the S-TSH response to thyroliberin was high borderline. She remained euthyroid during follow-up. The results suggest an annual incidence of spontaneous hypothyroidism of 1-2 cases per 1000 middle-aged females in Swedish west-coast population.