Clinical and Ultrasonographic Characterization of the Transition from Hashimoto Thyroiditis to Graves' Disease: A Long-term Follow-up Study.

PURPOSE: Conversion of Hashimoto Thyroiditis (HT) to Graves’ disease (GD) is uncommon. Patients experiencing this immunological transition have a milder form of hyperthyroidism. Nevertheless, US features, clinical course and outcome of thyroid function during long term follow up of these patients have not been systemically characterized so far.

METHODS

41 patients with conversion from HT to GD were compared with 214 patients with GD. Demographic, clinical and hormonal data as well as thyroid ultrasound (US) features, remission and relapse rates were evaluated.

RESULTS

TSH concentrations were significantly lower and fT4 and fT3 higher in GD compared to the switchers, despite lower TRAb levels. A higher number of switchers achieved remission with a first ATD course compared to GD patients. The number of patients achieving final remission with medical therapy was significantly higher in the switchers and remission was achieved in lower mean time and with lower mean dose of ATD; conversely, a higher number of GD patients required definitive ablative therapy. The switchers had a significantly higher prevalence of spontaneous early hypothyroidism following ATD treatment. Thyroid US evaluation showed significantly higher prevalence of thyroid hypotrophy and reduced parenchymal vascularization and a significantly lower prevalence of multinodular thyroid glands in the switchers compared to GD patients.

CONCLUSIONS

Autoimmune thyroiditis shifting from Hashimoto to Graves’ disease is characterized by a distinct clinical-ultrasonographic phenotype and clinical course of hyperthyroidism. Strict monitoring of thyroid function is required in these patients as both hyperthyroidism recurrence and early spontaneous return to hypothyroidism are common.