RESUMO
INTRODUCTION: Graves' disease is an autoimmune disorder. Goiter and Graves' orbitopathy are frequently seen clinically. It would be helpful for the diagnosis, grading, prognosis, and treatment of this condition if it was possible to find serum biomarkers to establish a connection between the plasma levels of these compounds and orbital changes. METHODS: A retrospective study was performed by revising the medical records of 44 patients with Graves' orbitopathy and 15 controls. The Osirix software (Pixmeo, Geneva, Switzerland) was used for manual orbital measurements. Plasma levels of Graves' orbitopathy substances were obtained in the analytical review of the patients. RESULTS: A greater muscle volume was observed in patients with Graves' orbitopathy in relation to the control group (p < 0.001). The clinical activity score (CAS) was associated to total muscle mass (p = 0.013) and retrorbital fat (p = 0.048). Our results indicated a direct relationship between serum concentrations of anti-thyroid peroxidase antibodies and inferior rectus thickening (p = 0.036); however, we did not observe a positive correlation between other muscle volumes and serum concentrations of various thyroid-related substances. CONCLUSIONS: This study is the first that uses Osirix measurement software to manually assess orbital features in patients with Graves' orbitopathy. These measurements were compared to the outcomes of tests performed in a laboratory. Among several serum biomarkers, anti-thyroid peroxidase appears to be a reliable biomarker that correlates positively with inferior rectus muscle thickness in patients with thyroid eye disease. This may help to improve the management of this disease.