Longitudinal association of thyroid-stimulating immunoglobulin levels with clinical characteristics in thyroid eye disease

Objectives The clinical course of thyroid eye disease (TED) is heterogeneous and predicting patients who may develop the severe sequelae of the disease is difficult. In this study, we evaluated the longitudinal association between changes in serum thyroid-stimulating hormone (TSH) receptor antibody (TRAb) levels and course of disease activity and severity over time. Design This was a multicentre, prospective, observational study. Setting Fifteen tertiary care oculoplastic service centres in Korea. Participants Seventy-six patients with newly diagnosed TED were included and followed up for 12 months. Methods We evaluated clinical characteristics and serum TRAb levels at baseline, 6 and 12 months of TED diagnosis. Additionally, we analysed longitudinal associations between the serum TRAb levels and clinical activity score (CAS), no signs or symptoms, only signs, soft tissue involvement, proptosis, extraocular muscle involvement, corneal involvement, sight loss (NOSPECS) score and proptosis. Results Thyroid-stimulating immunoglobulin (TSI) and TSH-binding inhibitory immunoglobulin (TBII) levels decreased during the 1-year follow-up, whereas disease activity measured using CAS decreased mainly in the first 6 months. Disease severity measured using NOSPECS score and proptosis remained unchanged. Moreover, inter-person differences in TBII levels were associated with CAS, NOSPECS score and proptosis over time, whereas inter-person differences in TSI levels were associated with NOSPECS score. Subgroup analysis of patients with a baseline CAS >= 4 demonstrated that within-person changes in TSI levels affected the CAS and NOSPECS score. Conclusions Follow-up measurement of serum TSI and TBII levels may help evaluate TED prognosis and enable accurate clinical decision-making.