ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2017) 50 P393 | DOI: 10.1530/endoabs.50.P393

Long-term relapse rates following thionamide withdrawal in Graves' thyrotoxicosis and the predictive role of TRAbs

Nyo Nyo Tun, Frase Gibb, Mark Strachan & Nicola Zammitt

Edinburgh Centre for Endocrinology & Diabetes, Edinburgh, UK.

Background: Thionamides are a safe and effective treatment for Graves’ thyrotoxicosis and tend to be favoured over radioiodine in the UK. Risk of recurrence following cessation of thionamides is high although most studies tend to have short duration of follow up. We have previously published follow-up data to 4 years in this cohort and now present follow-up out to 7 years.

Methods: Retrospective review of first presentation Graves’ disease where a course of thionamide was completed (n=282). Age, gender, smoking status, free T4, total T3, TRAb at diagnosis, TRAb at cessation of thionamide and time to normalization of thyroid function were assessed.

Results: Recurrent thyrotoxicosis occurred in 30% (84/282) at 1 year, 41% (113/273) at 2 years, 50% (130/259) at 3 years, 56% at 4 years (127/228), 62% at 5 years (101/163), 59% at 6 years (66/111) and 65% at 7 years (58/89). Logistic regression identified younger age and higher TRAb at cessation, as independent predictors of recurrence. 1 year after thionamide withdrawal, cessation TRAb <0.9 mU/L was associated with a 22% risk of recurrence compared to 46% when TRAb was ≥1.5 mU/L (P<0.001). The corresponding figures for 5-year recurrence risk were 54% and 73%, respectively (P<0.05). TRAb at diagnosis >12 mU/L was associated with a 79% risk of recurrence over 5 years compared to 47% when diagnosis TRAbs were < 5 mU/L (P=0.005).

Conclusions: This cohort provides the longest, well-characterised follow-up of a large number of patients with Graves’ disease after planned thionamide withdrawal. High TRAbs at diagnosis, and also at cessation of therapy, are indicative of a very high risk of recurrence. Only one-third of all patients will remain euthyroid in the long-term. In patients where recurrent thyrotoxicosis would be particularly hazardous, early consideration should be given to primary radioiodine therapy.

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