Age May Influence the Impact of TRAbs on Thyroid Function and Relapse-Risk in Patients With Graves Disease.

CONTEXT Thyrotropin receptor antibodies (TRAbs) play a crucial role in the pathogenesis of Graves disease (GD). However, factors that influence the association of TRAbs with thyroid hormones and relapse risk in GD remain unclear. OBJECTIVE We investigated the associations of TRAbs at diagnosis with thyroid hormones and relapse risk and potential factors that can influence these associations in GD. DESIGN AND SETTING A prospective study in an endocrine center in England. PATIENTS AND MAIN OUTCOME MEASURES Three hundred eighty-four consecutive patients with GD who had measurements of TRAbs and thyroid hormones at diagnosis. The association of TRAbs with thyroid hormones and relapse risk was assessed through linear regression and Cox proportional hazard models, adjusted for confounders. RESULTS TRAbs were nonlinearly associated with thyroid hormones, following a curve with an initial positive slope and a subsequent flattening (P < 0.0001). Higher TRAbs were associated with greater relapse risk [hazard ratio (HR), 1.05 (95% CI, 1.02 to 1.08) per 1-U/L increase]. These associations were modified by age, but not by sex, race, smoking, or thyroid peroxidase antibody levels. In younger participants, increasing TRAbs were associated with higher thyroid hormones and greater relapse risk [HR, 1.13 (95% CI, 1.04 to 1.23) per 1-U/L increase]. In older participants, TRAbs were not associated with thyroid hormones or relapse risk [HR, 0.99 (95% CI, 0.93 to 1.05) per 1-U/L increase. CONCLUSIONS In GD, age can influence the effect of TRAbs on thyroid function and relapse risk. TRAbs at diagnosis have better predictive value in younger patients with GD.