Endocrine Abstracts

A prolonged course of antithyroid drugs (ATD) is commonly used as first line treatment in patients with hyperthyroidism, although long term cure rates are poor – 40–50%. We performed a longitudinal analysis of outcomes in patients treated with a complete course of ATD and identified factors predicting remission.

583 consecutive patients with newly diagnosed hyperthyroidism presenting between 2005 and 2014 and treated with ATD for a minimum of 6 months were retrospectively analysed. Remission, defined as biochemical euthyroidism for a minimum of 6 months following ATD discontinuation, was achieved in 322 (55%). Among the remaining, 170 (29%) were given definite treatment with radioiodine or surgery, 76 (13%) stayed on a long-term ATD and 15 were lost for follow-up or died.

Binary logistic regression indicated that younger patients (AOR=1.03/per year; P<0.001) were more likely to achieve remission whereas ATD had lower likelihood of success in smokers (AOR=3.6; P<0.001), those with medium/large goitres (AOR=5.9; P<0.001) and subjects with thyroid eye disease (AOR=1.7, P=0.04). Gender, biochemical severity of hyperthyroidism at presentation, presence of TPO antibodies or family history of thyroid disease did not significantly influence the likelihood of remission.

Subsequently we determined remission-free survival during 36 months following treatment completion in those achieving remission (n=322). 75 (23%) subjects relapsed, most frequently during the first year following treatment (n=41). In univariate Cox regression models, the severity of hyperthyroidism at presentation (HR=1.01 per pmol/l; P=0.02) and presence of medium/large goitre (HR=2.1; P=0.03) significantly predicted risk of relapse at any point of follow-up period.

Conclusion: Medical therapy of hyperthyroidism with thionamides is associated with poor remission rates and high risk of relapse during follow-up. Patients with larger goitres, those with thyroid eye disease, subjects with more severe hyperthyroidism and smokers are less likely to be cured and early consideration of definitive treatment is needed in these subgroups.