Teprotumumab may reduce the cross-sectional area of the extraocular muscle


Teprotumumab is an infusion that has been shown to decrease proptosis in patients with thyroid eye disease (TED). While it has been theorized that proptosis reduction is due to decreased extraocular muscle (EOM) size, this has not been fully quantified.

Study design

This retrospective, noncomparative study of 24 patients with TED examined computed tomography measurements of EOM cross-sectional areas (CSAs) before and after 8 infusions of teprotumumab. The largest area was used for each muscle; this location was not always identical pre- and post-treatment.


Most patients (21 of 24) showed reductions in total EOM-to-orbit CSA ratios; the other 3 patients showed no improvement after treatment. Reduced EOM CSAs were significantly associated with diplopia reduction and EOM motility.


The study was limited by its small size and retrospective nature. As the authors discuss, there was inconsistent timing of pre- and post-treatment imaging, as well as variability in prior TED treatments (e.g., oral or intravenous steroids, rituximab). Additionally, there was no comparative arm, so it is difficult to draw any definitive conclusions.

Clinical significance

As teprotumumab is a relatively new treatment for TED, it is helpful to note that teprotumumab may play a role in decreasing TED-related EOM enlargement. This study’s findings provide information for patients and doctors to better understand how teprotumumab fits in with alternative, more cost-effective therapies to ameliorate the proptosis, strabismus, and diplopia that stem from TED.

Financial Disclosures: Dr. Anne Barmettler discloses no financial relationships.

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