Aim: Anti-thyroid treatment with carbimazole or propylthiouracil is the first-line treatment for autoimmune thyrotoxicosis in the UK. Following 1218 months treatment there is a significant relapse rate (at least 50%). This study analysed the demographics and clinical features of 100 patients with relapsed thyrotoxicosis to examine which variables are predictive of relapse.
Methods: This retrospective study included adult patients identified using our electronic database of patients seen in thyroid clinic between 1st June 2018 and 1st June 2019. Clinical details and biochemical values obtained from electronic records were analysed using descriptive statistics and logistical regression.
Results: Of 100 patients, 77% were female, with 21 different ethnic origins, predominantly White/British. The average age of first presentation of thyrotoxicosis was 39 years (range 1678 years). Of those who had TSH-R Ab levels available, 99% were elevated at diagnosis; the concentration of which directly correlated to time interval between relapse (P = 0.03; those with the highest concentration relapsing sooner). 46% had documented goitre at initial diagnosis and 9% had documented eye disease. There was also a correlation with duration of first treatment and time interval to relapse (P = 0.004, those with shortest duration of treatment relapsed most quickly). 12% relapsed whilst on a low dose anti-thyroid medication (5 mg CBZ or equivalent).
Conclusion: Our study demonstrates a significant correlation between initial TSH-R Ab concentration and duration of initial treatment determining the time interval for relapse. We found no correlation between the presence of goitre and the sample size was too small to assess the relationship with TED. Further research into factors determining relapse in Graves disease should be established and reliable scoring models need to be developed for predicting relapse in individual patients to guide long-term therapy.