The effect of radioiodine and antithyroid drugs on serum long acting thyroid stimulator protector (IATS-P). A three year prospective study.

Over a three year period we have studied the effect of either a one year course of Carbimazole or a single dose of radioiodine in a group of 46 patients with Graves' disease. Initially, in untreated patients LATS-P was present in 39 (85%) but at the end of the study was only detectable in 19 (41%). The clinical outcome in 29 patients initially treated with carbimazole correlated well with changes in serum LATS-P which persisted in 18. Thirteen of these ultimately required radioiodine or sub-total thyroidectomy. With radioiodine two patterns of response were seen, in some LATS-P levels declined, whereas in others transient increases were seen usually during the first year but subsequently fell. There was no difference in clinical response between the two groups. Overall, the study indicates that serum LATS-P is related to the clinical course of Graves' disease but there remains a minority of patients in whom the activity cannot be detected.