Endocrine Abstracts

Hyperthyroidism has been linked to long-term cardiovascular and metabolic morbidity and increased mortality. We aimed to assess differences in mortality and cardiometabolic outcomes depending on treatment modality to better inform patient-clinician decision-making.

Methods: We identified 62,474 patients with newly diagnosed hyperthyroidism, treated with antithyroid drugs (ATD), radioiodine or thyroidectomy from a UK population-based GP database (>16M patients). Health records were linked with Hospital Episode Statistics, Office for National Statistics mortality data, and Index of Multiple Deprivation. All-cause mortality, major cardiovascular events (MACE: cardiovascular death, heart failure or stroke) and post-treatment obesity diagnosis were studied. A “target trial” approach was used to elucidate causal effects. Average treatment effects (ATE) were estimated using inverse-probability weights with regression adjustment. Mortality was assessed as time-to-event; other outcomes were modelled as binary (funding: NIHR RfPB, NIHR200772).

Results: Patients treated with ATD comprised 73.4% of the cohort; 19.5% were treated with radioiodine, and 7.1% with thyroidectomy. Patients were followed for a median of 10 years (IQR: 6-15). Estimated mean survival was 11.7 years with ATD treatment. Definitive treatment increased survival: radioiodine by 1.7y. (95%CI: 1.1-2.4; P<0.001) and thyroidectomy by 1.4y. (0.5-2.4; P=0.003). The estimated risk of MACE if the population were treated with ATD was 9.9% (9.6-10.3), which increased by an additional 0.7% (0.1-1.3; P=0.02) with radioiodine but not with thyroidectomy (0.02% [(-0.8)-1.2], P=0.7). The estimated risk of post-treatment obesity was 7.6%, which increased by 0.9% (0.3-1.6, P=0.005) with radioiodine and 1.7% (0.5-2.8, P=0.003) with thyroidectomy.

Conclusion: EGRET is the first large study using population-based linked community and hospital data to elucidate the long-term consequences of treatment modalities for hyperthyroidism. We confirmed a decreased mortality in patients undergoing definitive treatment whereas a slightly increased risk of obesity was found in patients treated with radioiodine and surgery. Compared to medical treatment, a small increase in cardiovascular events was noted with radioiodine.