Thyrotrophin Receptor Antibody Concentration And Activity, Several Years After Treatment For Graves’ Disease

Summary

Objective

TSH receptor antibodies (TRAb) are responsible for autoimmune hyperthyroid disease (Graves' disease; GD) with TRAb levels tending to decrease following treatment. Measurement of TRAb activity during follow up could prove valuable to better understand treatment effectiveness.

Study Design

TRAb concentration and stimulating (TSAb) and blocking (TSBAb) activity of patient serum were assessed following different treatment modalities and follow up length.

Methods

Sixty‐six subjects were recruited following treatment with carbimazole (n=26), radioiodine (n=27) or surgery (n=13). TRAb, TPO‐Ab, Tg‐Ab and GAD‐Ab were measured at a follow up visit as well as bioassays of TSAb and TSBAb activity.

Results

Forty five percent of all patients remained TRAb positive for more than one year and 23% for more than 5 years after diagnosis, irrespective of treatment method. Overall, TRAb concentration fell from a median (IQR) of 6.25 (3.9‐12.7) to 0.65 (0.38‐3.2) U/L. Surgery conferred the largest fall in TRAb concentration from 11.4 (6.7‐29) to 0.58 (0.4‐1.4) U/L. Seventy percent of TRAb positive patients were positive for TSAb and 1 patient (3%) was positive for TSBAb. TRAb and TSAb correlated well (r = 0.83). In addition, 38/66 patients were Tg‐Ab positive, 47/66 TPO‐Ab positive and 6/66 were GADAb positive at follow up.

Conclusions

TRAb levels generally decreased after treatment but persisted for over 5 years in some patients. TRAb activity was predominantly stimulatory, with only one patient demonstrating TSBAb. A large proportion of patients were Tg‐Ab/TPO‐Ab positive at follow up. All treatment modalities reduced TRAb concentrations, however surgery was most effective.

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