Endocrine Abstracts

Introduction and aims: Thionamide may have immunosuppressive mechanisms. However, data suggest restoration of the immunological regulation as patients return to the euthyroid state may better explain remission, How successfully patients are kept euthyroid during a course of antithyroid drug therapy for Graves’ hyperthyroidism, and whether not continuously maintaining normal thyroid function is associated with a worse prognosis, is not known.

Aims: 1) assessment of duration of euthyroid, subclinical and overt hyperthyroid periods during thionamide therapy of newly diagnosed Graves’ disease, 2) thyroid function with shorter (2–4 weeks) compared to longer (5–6 and >7 weeks, respectively) intervals between out-patient visits, and 3) whether periods of hyperthyroidism are associated with lower remission rates.

Methods: Retrospective anaylsis of N=301 patients treated with thionamides for ≥10 months at a single thyroid out-patient unit from 2010 to 2015, patients in remission (N=156) compared to those with relapsing hyperthyroidism (N=145) – median follow-up after stopping thionamides 20 and 14 months, respectively. Multivariant regression analysis including length of different thyriod functions, scheduled intervals between visits, and other factors such as age, TRAb, degree of hyperthyroidism at first diagnosis, time to normalization of fT4 after initiation of antityhroid drug therapy, or smoking status to define independent predictors of remission.

Results: Median treatment duration (15.0 vs. 15.6 months) was comparable (P=n.s.). Relapsing patients displayed longer (P<0.0001 and p<0.05, respectively) periods of overt (11±3.5 vs. 2.6±3.3 weeks) and subclinical (10.4±2.3 vs. 8.3±4.2 weeks) hyperthyroidism, and shorter (P<0.0001) periods with normal thyroid function (33.9±12.4 vs. 46.8±12.1 weeks). Scheduled intervals differed widely within patients (2 to >7 weeks), were not different between groups, and did not influence thyroid function. Normal thyroid function at >50% of all visits was observed more frequently (92.3 vs. 64.1%) and at ≤5% and 6–20% of all visits less (P<0.0001, respectively) frequently (0% and 0% vs 3.4 and 4.8%, respectivley) in remitting patients than in those who relapsed. Overt hyperthyroid and euthyroid periods were independent (opposing) predictors of remission, respectively, as were age, TSHR-Ab, fT4 at first visit, and time to first normalization of thyroid function.

Conclusion: Continuously maintaining normal thyroid function during antithyroid drug therapy may be associated with increased remission, whereas overt hyperthyroid periods with higher relapse rates. Intervals between visits >7 weeks were not associated with unfavourable outcome and identified, on an individual patient’s basis, more often with patients in remission.