MON-420 Higher serum levels of MMP-9 related to intraconal fat in active Thyroid Eye Disease

Abstract Disclosure: C. Minatel Riguetto: None. R. Luccas: None. F. Mota Gonzalez: None. C. Abbehusen Lima Castelo Branco: None. E. Buzolin Barbosa: None. M. Alves: None. F. Reis: None. D. Engelbrecht Zantut Wittmann: None. Purpose:This study aimed to identify relevant orbital magnetic resonance imaging (MRI) findings in subjects with Graves' disease (GD) at different stages of thyroid eye disease (TED) and to relate these findings to clinical and laboratory assessments.Methods:Twenty-four subjects with GD were subdivided into active TED (n=9), GD with inactive TED (n=7), GD without apparent TED (n=8), and 13 healthy control subjects without evidence of autoimmune thyroid disease were examined. Orbital MRI was performed on a 3.0 Tesla MR unit between 2019 and 2021. MRI measured extraocular muscles, proptosis, intraconal and extraconal fat, which were then related to clinical and laboratory findings (serum MMP-2, MMP-3 and MMP-9). MRI scans were assessed by two experienced neuroradiologists blinded to the clinical examinations. Results: There were no significant differences in demographic characteristics between the groups. The active TED group demonstrated higher bilateral ophthalmometry and Clinical Activity Score (CAS) compared to other groups. The right and left superior rectus muscles were enlarged in the active TED subjects compared to other groups (p=0.0308). Similar findings were observed with the right inferior rectus (p=0.0305). Although the active TED group had higher ophthalmometry on clinical assessment, the inactive TED group exhibited higher rates of right and left proptosis than other groups (p=0.0019 and p=0.0020). No significant enlargement of other EOMs was found. Intraconal fat was increased in the active TED group (p=0.0014), while extraconal fat was increased in the inactive TED group compared to the other groups (p=0.0201). Subjects with increased intraconal fat presented more eyelid erythema (p=0.0357) and significantly higher serum levels of MMP-9 (p=0.0460). Conjunctival redness showed a positive correlation with enlargement of the superior and inferior rectus. No significant correlation was found between CAS and the MRI findings. Conclusion: This study demonstrated that subjects with active TED had increased EOM enlargement, particularly of the superior and inferior rectus muscles. Although no correlation with CAS was found, conjunctival redness was positively associated with rectus enlargement. Furthermore, intraconal fat was significantly increased in active TED and was linked to higher serum levels of MMP-9 and eyelid erythema. These findings support the hypothesis that MMP-9 could play a role in the pathogenesis of TED. Presentation: Monday, July 14, 2025