Ten Year Outcome of Anti-Thyroid Drug Treatment for First Episode Graves' Thyrotoxicosis: The Predictive Importance of TRAb.

OBJECTIVE

To establish the risk and time course of recurrent thyrotoxicosis following withdrawal of anti-thyroid drugs (ATD) and risk factors for recurrence.

DESIGN

Single-centre retrospective study.

METHODS

Two hundred and ninety people with a first episode of Graves' thyrotoxicosis, who completed a course of ATD, were included. Clinical and biochemical parameters associated with recurrence risk were assessed over a 10-year period.

RESULTS

Recurrence occurred in 54% of individuals over a 10-year period, with 73% occurring within 2 years. Younger age (41 years [33-51] vs. 47 [39-56], p = 0.011), higher TSH receptor antibody (TRAb) at diagnosis (8.8 IU/L [4.9-17.2] versus 6.0 [4.1-9.9], p = 0.002), higher TRAb at cessation of ATD (1.3 [<0.9-2.3] vs. 1.0 [<0.9-1.3], p < 0.001), longer time to normalisation of TSH (6 months [3-9] vs. 4 [2-7], p 0.013) and longer time to normalisation of fT4 (2 months [1-3] vs. 1 [1-2], p = 0.001) were all associated with relapse within 10 years. Recurrence within 10 years occurred in 74% of individuals with TRAb > 12 IU/L at diagnosis but only 44% of those with TRAb < 5 IU/L at diagnosis (p = 0.001). TRAb (at diagnosis and cessation) and age were independently associated with relapse in multivariate analysis.

CONCLUSIONS

Most recurrent thyrotoxicosis occurs within the first few years after ATD withdrawal. TRAb concentration, at diagnosis and cessation of ATD, is a useful predictor of recurrence risk and can be used to inform decisions on the optimal approach to primary therapy.