These results indicate that the occurrence of thyroid hormone autoantibodies among the healthy Japanese population is fairly common. However, interference of thyroid hormone autoantibodies in the radioimmunoassay of free thyroid hormones is exceptional.

We present two cases of Graves' disease whose initial thyroidal scintiscan with 99mTcO4- (Case 1) and 123I (Case 2) showed unilateral diffuse uptake of radioisotopes. Initial diagnosis was possibility of malignancy in Case 1 and Graves' disease or Plummer's disease in Case 2. Both cases underwent right hemithyroidectomy. Histopathology of the resected thyroid gland in both showed hyperplastic columnar epithelium and infiltrative lymphocytes which was compatible with Graves' disease. Twenty seven (Case 1) and eight months (Case 2) after operation, both presented with thyrotoxic symptoms associated with enlarged left lobe, increased serum free thyroid hormone concentrations, suppressed TSH concentration, increased thyroidal 123I uptake in the remaining left lobe, and positive thyrotropin receptor antibodies. Both cases were successfully treated with methimazole. It was concluded that initial radioisotope uptake as well as scintigram in rare subgroup of patients with Graves' disease could be similar with that of non-autoimmune autonomous goiter (Plummer's disease).

The prevalence of increased titres of antibodies to Yersinia enterocolitica (serotype 3) has been studied in sera from patients with various thyroid diseases. In contrast to the low prevalences of the antibodies in healty subject (24.3%), titres (greater than 10) of anti-Yersinia enterocolitica (anti-Yersinia) were found more frequently in patients with thyroidal disorders, especially in Graves' disease (70.0%). Furthermore, high titres of the antibodies (greater than or equal to 160) were found only in patients with Graves' disease. There was no significant correlation between the titers of anti-Yersinia antibodies and those of anti-TSH receptor antibodies in sera from patients with Graves' disease. In seven individual samples of sera, the anti-Yersinia antibody titer was high before treatment, but the decrease in the anti-TSH receptor antibody titer following treatment was associated with a simultaneous decline in anti-Yersinia antibodies in all of them. A highly positive and significant correlation between the titers of anti-TSH receptor antibodies and anti-Yersinia antibodies was obtained in each of them. These findings could be merely a reflection of the measurement of the cross-reaction of anti-Yersinia antibodies with anti-TSH receptor antibodies but the possibility of an association between Yersinia infection and the production of anti-TSH receptor antibodies in at least some patients with Graves' disease cannot be ruled out.

Serum concentration of osteocalcin (OC) was measured in sera from untreated patients with Graves' disease, hypothyroidism due to Hashimoto's thyroiditis, and subacute thyroiditis. Serum concentration of OC in Graves' disease and hypothyroidism were 14.1 +/- 5.6 micrograms/L and 3.8 +/- 2.7 micrograms/L, respectively which were significantly different from that of healthy subjects (Graves' disease, p less than 0.001, hypothyroidism, p less than 0.01). Serum concentration of OC in patients with subacute thyroiditis was 8.0 +/- 3.5 micrograms/L which was not statistically different from age-matched normal controls. Serial measurement of serum OC for 24 mo in 15 patients with Graves' disease after initiation of antithyroid drugs disclosed that the decline of serum OC was obtained only 24 mo after antithyroid drug therapy. On the other hand, in hypothyroid patients, increased serum OC was observed after 1-2 months treatment of L-T4. Correlation coefficients between serum concentrations of OC and T3, T4, FT3 or FT4 in all the patients with thyroid disorders were 0.66, 0.51, 0.50 and 0.54, respectively, which were statistically significant (all, p less than 0.001). These results suggest that osteoblastic activity is enhanced in hyperthyroidism and suppressed in hypothyroidism. In hyperthyroid patients, despite of normalization of FT4 concentration in relatively short period (within 3-4 mo), it took 24 mo after initiation of antithyroid drugs for OC to normalize, suggesting not only thyroid hormone per se but also some unknown factor(s) participates in serum OC secretion. In contrast to thyrotoxic patients, rapid increase in serum OC after initiation of supplemental L-T4 treatment in hypothyroidism was observed, suggesting a direct effect of thyroid hormone on the osteoblasts in patients with hypothyroidism.

A 40-year-old housewife was referred to our hospital for evaluation of a thyrotoxic state. A month after rubella infection, she developed heat intolerance. Physical examination revealed a hard and non-tender goiter with no signs or symptoms of inflammation. Free thyroid hormones were high and TSH was undetectable. 123I-thyroidal uptake was suppressed. Antithyroglobulin and anti-microsomal antibodies were negative throughout the course. A serologic study revealed high levels of anti-rubella antibodies. After a month without any treatment, she became euthyroid. Free thyroid hormones and TSH gradually became normal and the antibodies to rubella decreased. 123I-thyroidal uptake increased. From the clinical course, the patient was diagnosed as having silent thyroiditis. We suggest that viral infection such as rubella could cause the development of silent thyroiditis.