[Occurrence of immune hyperthyroidism after radioiodine therapy of autonomous goiter]

The goal of the study was to examine the prevalence of Graves' disease following I-131 treatment of autonomous goiter with special regard to pretreatment scintigraphic patterns.

Pre- and posttreatment in-vitro and in-vivo parameters were studied in 375 consecutive patients treated with I-131 therapy for nodular or diffuse autonomous goiter. All patients included were within ambulant control for at least 2.5 months following treatment. According to the pretreatment Tc-99m pertechnetate scan 59% (220/375) had multifocal (MF), 23% (86/375) unifocal (UF), 10% (38/375) mixed focal-disseminated (FD) and 8% (31/375) disseminated (D) scintigraphic patterns.

In 93.9% (352/375), the autonomous tissue was totally, in 2.1% (8/375) partially and in 1.6% (6/375) insufficiently eliminated. In 2.4% (9/375) a relapse of hyperthyroidism was observed 2 to 10 months following I-131 therapy. In 8 patients a relapse of hyperthyroidism was accompanied or followed by an elevation of the previously non-elevated TSH-receptor antibody (TRAb) level and in 1 patient by an TRAb increase to the upper borderline range implicating Graves' disease. With the prevalence of Graves' disease following I-131 therapy a statistically significant difference in pretreatment Tc-99m pertechnetate scintigraphic patterns was found: 0% of unifocal (0/86) or multifocal (0/220), however 18% (7/38) of focal-disseminated and 7% (2/31) of disseminated scintigraphic patterns. From the 366 patients without relapse of hyperthyroidism 2 (MF) had elevated pre- and posttreatment TRAb levels and 3 (D) had elevated TRAb levels for the first time after I-131 therapy.

There is a low overall prevalence (2.4%) of Graves' disease following I-131 therapy for nodular or diffuse autonomous goiter. However, the prevalence of posttreatment Graves' disease is highly dependent upon pretreatment scintigraphic patterns exhibiting focal-disseminated or disseminated patterns.