Differential evolution of thyroid peroxidase and thyrotropin receptor antibodies in Graves' disease: thyroid peroxidase antibody activity reverts to pretreatment level after carbimazole withdrawal.

In this study, we compared the evolution of thyroid peroxidase antibody (TPOAb) and thyroid-stimulating antibody (TSAb) activities before, during, and after treatment of Graves' disease (GD) with carbimazole. TPOAb and TSAb were measured in sera from 75 patients with GD, during an 18-month block-replace regimen and after drug withdrawal (12, 24, and 36 months). At diagnosis, TPOAb were present in 85% of the patients versus 99% for TSAb. During the treatment, TPOAb values and prevalence significantly decreased, as observed with TSAb. After drug withdrawal, TPOAb levels increased once again to reach the pretreatment values, whereas TSAb remained unchanged. TPOAb values and prevalence at drug withdrawal were not significantly different between patients who remained euthyroid and those who had a relapse of hyperthyroidism. In contrast, TSAb values and prevalence were higher at drug withdrawal in relapse patients. In conclusion, TPOAb and TSAb changes are similar during GD treatment by carbimazole but diverge after drug withdrawal. TPOAb might reflect autoimmune perturbations independently of the clinical status and of the thyroid-stimulating activity.