THYROID-ASSOCIATED OPHTHALMOPATHY IN A HYPOTHYROID PATIENT.

Thyroid-associated ophthalmopathy (TAO) is an autoimmune disorder of the orbit that occurs predominantly in Grave's hyperthyroidism, while it is an uncommon clinical finding in patients with Hashimoto's thyroiditis (HT) and hypothyroidism. We report the case of a 62-year-old female patient who presented with left eyelid edema, proptosis, diplopia, and lateral paralysis of the left eye. Magnetic resonance imaging of the orbits showed retrobulbar mass in the left orbit with hyperintense signals within left medial rectus muscle, offsetting but not infiltrating the optic nerve. An ¹⁸F-fluorodeoxyglucose positron-emission tomography/computed tomography (18F-FDG PET/CT) scan revealed pathological ¹⁸F-FDG uptake of expansive mass within rectus medialis muscle of the left eye (SUVmax=11.0) and similar findings in the right eye (SUVmax=7.1). It also displayed increased glucose metabolism in the thyroid gland (SUVmax=6.4). Laboratory findings showed increased thyrotropin level, while thyroid-stimulating-hormone-receptor antibodies were negative. The patient was diagnosed with HT and TAO, so levothyroxine therapy was introduced. Gradual improvement of TAO symptoms was attained a year later. Diplopia subsided and the patient regained complete eye movements. In conclusion, correction of hypothyroidism can significantly improve symptoms of TAO. Additional value of this case report lies in ¹⁸F-FDG PET/CT images displaying increased metabolic activity, which can advance clinical evaluation; however, further research is needed.