[Measurement of thyroid autoantibodies in Graves' disease.]

It is thought that dietary iodine may play a role in thyroid autoimmune reactivity. Iceland is an iodine rich area and therefore it seemed interesting to measure autoantibodies against TSH receptor (TRAb), thyroid peroxidase (TPO) and thyroglobulin (TG) in Icelandic patients with Graves' disease. Serum samples were collected from 47 patients with untreated Graves' disease, 73 patients with Graves' disease that had been treated with radioiodine (U1I), most of them (56) hypothyroid following the treatment and therefore on T4 replacement, others euthyroid. Measurements were also done on samples from a reference group of 74 healthy volunteers. All reference values are 0.95 fractile. Untreated patients with Graves' disease had TRAb values over reference range in 68.1% of cases being similar to what others have observed. The untreated patients with Graves' disease had TPO antibody measurement positive in 50.0% of cases and TG antibodies in 34.7%. This is much lower frequency of positive tests than observed elsewhere when measured with ELISA. Although methodological factors might play a role, this difference could also be explained by difference in iodine intake. The antibodies were less frequent in radioiodine treated patients than in the untreated ones. This is in agreement with the observation that serum levels of these antibodies tend to decrease with time from treatment. The antibody measurements did not differentiate between radioiodine treated patients with Graves' disease needing T4 replacement and those who did not.