A 76-year-old man with double vision turned out to have thyroid eye disease — despite normal thyroid hormone levels. His case highlights how TED can present even in euthyroid patients, and how risk factors like smoking and vitamin D deficiency play a key role. Treatment decisions were complicated by baseline hearing loss, ruling out the only FDA-approved therapy.
A 76-year-old man with a 3-week history of binocular vertical diplopia was ultimately diagnosed with moderate euthyroid thyroid eye disease (TED) — a condition most clinicians associate with an overactive thyroid. Despite normal thyroid hormone levels, elevated thyroid stimulating immunoglobulin and thyroglobulin antibodies, along with MRI findings showing enlargement of the left inferior rectus and medial rectus muscles with tendon sparing, pointed to TED as the culprit.
TED is an autoimmune condition driven by thyroid-related autoantibodies that trigger orbital fibroblast activation, leading to extraocular muscle expansion and, in some cases, sight-threatening complications. While most patients are hyperthyroid at presentation, 5–10% are euthyroid. Older age, male sex, and smoking are associated with more severe disease — all factors present in this patient.
Key Takeaways:
Why it matters: This case is a reminder that TED doesn't always come with thyroid dysfunction. Clinicians should keep TED on the differential for orbital myopathy even in euthyroid patients, and carefully weigh treatment options given the significant side effect profiles involved.
