[Paradoxical effect of radioiodine therapy in functional thyroid autonomy and mild immunothyropathy]

To examine all cases with Graves' disease after radioiodine therapy of autonomously functioning thyroid tissue (AFFT) in order to find the cause.

We retrospectively studied 1428 pts who were treated between 11/93 and 3/97 with radioiodine for AFTT and who underwent at least one control examination.

15 (1.1%) of all pts developed Graves' disease 8.4 (4-13) months after radioiodine therapy. There was no direct suggestion of Graves' disease (TRAK negative, no endocrine ophthalmopathy) in any pt at the time of radioiodine therapy. More detailed analysis of anamnestic data, however, revealed evidence that immunothyropathy predated radioiodine therapy in 11 of the 15 pts. Paradoxical effects of radioiodine therapy manifested as an increase in immunothyropathy in 14 pts, a deterioration in metabolism in 11 pts and a first occurrence of endocrine ophthalmopathy in 5 pts.

Exacerbation of preexisting, functional primarily insignificant immunothyropathia is held responsible in most cases for the observed paradoxical effects after radioiodine therapy, resulting in radiation-induced manifest Graves' disease; however no therapeutical consequences are recommended.