Thyroid stimulating antibodies are highly prevalent in Hashimoto's thyroiditis and associated orbitopathy

Abstract

Context: Thyroid-associated orbitopathy (TAO) rarely occurs in patients with Hashimoto's thyroiditis (HT). Objective: There is evidence that TSH receptor stimulating antibodies (TSAb) play a role in the pathogenesis of TAO. In this report, the prevalence of TSAb in HT patients with and without TAO was studied. Design: This is a longitudinal observational study. Setting: The study took place in an academic joint thyroid-eye clinic. Subjects: A total of 1055 subjects were included. Methods: TSAb was measured with a Food and Drug Administration - cleared bioassay that uses Chinese hamster ovary cells expressing a chimeric TSH receptor and a cAMP response elementdependent luciferase. Results of TSAb activity were reported as percentage of specimen-to-reference ratio (SRR%, cutoff >140%). Main Outcome Measure: We measured the association of TSAb with the risk of TAO in patients with HT. Results: Of 700 consecutive and unselected patients with HT, 44 (6%) had overt TAO. Patients with HT+TAO were older (P < .001. Highest TSAb values were noted in patients with active and severe TAO vs those with mild and inactive TAO: 486, 392-592 vs 142, 73-192.5; < .0001), whereas the odds ratio per 10-fold change in TSAb SRR% (quantitative TSAb) was 133 (95% CI, 45-390, P < .0001). The area under the receiver operating characteristic curve for qualitative and quantitative TSAb was 87.2% (95% CI, 80.6-93.8) and 89.4% (95% CI, 84.1-94.7), respectively. Conclusions: TSAb is strongly associated with TAO in HT and TSAb may contribute to the pathophysiology of TAO.