SAT-607 "Eye" Spy with My Big Eye: Thyroid Ophthalmopathy Secondary to Hashitoxicosis

Introduction: Hashitoxicosis is the transient hyperthyroid phase of chronic autoimmune thyroiditis, common in children. It is characterised by mild-moderate symptoms of hyperthyroidism, small painless goiter and normal or slightly increased uptake on thyroid scintigraphy. It is differentiated from Graves’ Disease (GD) by its shorter course and absence of thyroid ophthalmopathy (TAO). We present a rare case of TAO associated with Hashitoxicosis in an adult. Case Presentation: A 55 year-old gentleman, with current tobacco use and family history of thyroid disease, presented with complaints of a bulging left eye and double vision for 3-6 months. He endorsed pain and fatigue of eye muscles, and dry eyes. Additionally, he endorsed weight gain, increased appetite, and flat affect. Examination revealed a 5 mm proptosis and restrictive strabismus of the left eye with a normal fundus bilaterally. The thyroid gland was normal to palpation. Laboratory tests revealed a TSH of 0.016 mcIU/ml (normal 0.358-3.800 mcIU/ml), total T3 of 90 ng/dl (normal 60-181 ng/dl) and total T4 8.2 mcg/dl (normal 4.7-13.3 mcg/dl). A TSH receptor antibody (TRAb) was normal (1.35 IU/l, normal <1.75 IU/l), while a thyroid peroxidase (TPO) antibody titre was elevated (5780.7 U/ml, normal <60.1 U/ml), confirming Hashitoxicosis. Thyroid scintigraphy showed normal uptake (4.25% at 4 hours, 24.1% at 24 hours) with a focal photopenic area in the left lower lobe suggesting a non-functioning nodule. A thyroid ultrasound showed mild generalised enlargement of the thyroid gland with hypervascularity and multiple 1 cm hypoechoic solid nodules bilaterally. Magnetic Resonance Imaging (MRI) of the orbit confirmed left sided TAO due to markedly enlarged inferior rectus and mildly enlarged medial and lateral recti. The patient was diagnosed with TAO due to Hashitoxicosis. He is currently awaiting an orbital decompression and strabismus surgery. Discussion: Initial release of preformed thyroid hormones from the inflamed thyroid gland leads to Hashitoxicosis. Traditionally, bilateral TAO with hyperthyroidism is considered pathognomonic for GD. In patients with unilateral TAO, Hashitoxicosis should also be considered. The pathophysiology of TAO due to Hashitoxicosis is not well-understood. Presence of low level TRAb may be implicated, however, more research is required to clarify the natural history of this condition. Current practice suggests that steroids and other immunosuppressive agents such as Rituximab may alleviate symptoms of TAO. Decompression surgery is considered for cases not responding to medical management. References: 1. Unnikrishnan A G. Hashitoxicosis: A clinical perspective. Thyroid Res Pract 2013;10, Suppl S1:5-6 2. Kırmızıbekmez H, Yeşiltepe Mutlu RG. Atypical Presentation of Hashimoto's Disease in an Adolescent: Thyroid-Associated Ophthalmopathy. J Clin Res Pediatr Endocrinol. 2014;6(4):262-5.