Endocrine Abstracts

Background: Graves’ disease (GD) is the commonest cause of primary hyperthyroidism. First-line treatment involves 12-18 months of anti-thyroid drugs (ATD). Subsequently, around 50% of patients will relapse, requiring definitive treatment. Identifying risk factors that predict relapse or treatment failure can guide management. We aimed to explore risk factors that identify patients at high risk of relapse or medical treatment failure, to allow prioritisation for definitive treatment.

Methods: We retrospectively evaluated data on consecutive patients with first presentation of GD who had positive TSH receptor antibodies (TRAbs >0.4 IU/l) at diagnosis at Royal Berkshire Hospital and required ATD, between February 2017-December 2018. Baseline demographics, TRAbs, thyroid function tests (TFTs) levels, and thyroid eye disease (TED) at diagnosis were recorded. RSR Elisa TRAb 2nd generation assay and Roche Cobas Elecsys Gen II assay were used to measure TRAB and FT4, respectively.

Results: We included 154 individuals: mean age 51.6 years, 71.4% female, 15% TED at diagnosis. The median (IQR) TRAb level was 2.7 (1.7, 5.7)IU/l, and median (IQR) FT4 level was 52.6 (30.3, 81.4) pmol/l. The median follow-up of TFTs was 48 months. Median duration of ATD was 18 months. 102 (66.2%) participants relapsed or had treatment failure (ATD duration>24 months). Gender and median TRAb values were similar in both groups. Subsequently, patients were divided into 3 sub-groups according to TRAb values (1st tertile: 0.5-1.9 IU/l, 2nd: 2.0-4.3 IU/l, 3rd: 4.4-31.0 IU/l). Individuals in the 3rd tertile vs. the 1st, had more often TED (30.4% vs. 11.1%, OR 3.5; P=0.05), higher FT4 levels (72.4 pmol/l vs. 31.6 pmol/l; P=0.0001), and significant risk of treatment failure (77.4% vs 54.2%, OR 2.9; P=0.02).

Conclusions: We showed that medical treatment failure or relapse is commoner in patients with TED, higher TRAb and FT4 levels, prompting early referral for definitive treatment.