SUN-569 Thyroid Associated Orbitopathy (TAO): An Unusual Presentation

Thyroid associated orbitopathy (TAO), frequently termed Graves ophthalmopathy, is part of an autoimmune process that can affect the orbital and periorbital tissue. The diagnosis of TAO is based on clinical orbital features, radiological criteria, and the potential association with thyroid disease. The orbital expression of the thyroid stimulating hormone receptor (TSHR) has been implicated in this condition which generally occurs in hyperthyroid patients due to Graves’ disease. In 20% of cases, patients are euthyroid or hypothyroid. The possibility of having different types of antibodies in Graves’ disease (stimulatory, blocking and/or neutral) can explain variations in thyroid function. Nevertheless, cases of TAO associated with Hashimoto’s thyroiditis (HT) have already been described. A 51-year-old non-smoker woman with a medical record of multinodular goitre and primary hypothyroidism under 75µg of levothyroxine complained of diplopia to her ophtalmologist. During the last 3-4 weeks, she described redness and swelling of the eyelids, foreign body sensation and blurred vision in her left eye. On physical examination, the ophthalmologist described a limitation on elevation of the left eye and vertical diplopia in levoversion. The patient was referred to the emergency department (ED) to perform a head and an orbit CT scan. The exam revealed: ‘…in relation to the left orbit, there is a clear thickening of the inferior rectus muscle and a less pronounced thickening of the medial rectus muscle. Aspects suggestive of Graves’ disease. The endocrinologist confirmed the patient medical record and excluded other signs/ symptoms of hypo/hyperthyroidism besides a weight loss of 5kg in the last 6 months. Analytical evaluation at the ER: TSH 0.002 µU/mL (N: 0.35-4.94), FT4 1.89 ng/dL (N: 0.7-1.48), FT3 5.87 pg/mL (N: 1.71-3.71). The levothyroxine was suspended and the patient initiated oral prednisolone 30mg/day, selenium 200µg/day and artificial tears. Two weeks later, the patient’s symptoms improved. Analytical evaluation: TSH receptor antibodies –TRAbs: 5.6U/L (N: 0-1.8), anti-thyroid antibodies: negative, TSH 0.002uU/mL (N: 0.35-4.94), FT4 1.64ng/dL (N: 0.7-1.48), FT3 4.30 pg/mL (N: 1.71-3.71). She continued corticosteroid therapy for 4 weeks and performed thiamazole during 8 weeks. Currently the patient is asymptomatic without medication. When TAO occurs in euthyroid or hypothyroid patients, the diagnosis is challenging. In this case report, the 9-year history of hypothyroidism pointed to the possibility of an orbitopathy associated with HT. However, the absence of anti-thyroid antibodies (anti TG and anti TPO) and the presence of TRAbs led the authors to the final diagnosis: Graves’ disease with thyrotropin-blocking antibodies (TBAb) and thyroid stimulating antibodies (TSAb). Although rare, a normal or subnormal thyroid function could not exclude the diagnosis of TAO.