Endocrine Abstracts

Introduction: Thyroid eye disease occurs in around one quarter of patients with Graves’ hyperthyroidism. However, it is rarely associated with primary hypothyroidism. We describe a case of a patient with thyroid eye disease secondary to primary hypothyroidism.

Case report: A 50-year-old female with known primary hypothyroidism was referred to Ophthalmology and Endocrinology in May 2024 with symptoms of thyroid eye disease, which have been present for several months. She was diagnosed with primary hypothyroidism in 2012 and has been on levothyroxine since. She was smoking approximately 20-30 cigarettes daily at the time of referral. We reviewed her and organised thyroid function tests and a thyroid ultrasound. Her TSH came back as suppressed with normal free T4 and free T3 levels. TSH receptor antibodies and thyroid peroxidase antibodies came back as positive at 19.4 IU/L (reference range 0.0-0.9) and 190.6 IU/ml (reference range 0.0-9.0) respectively. Thyroid ultrasound came back as unremarkable. Her levothyroxine dose was reduced due to a suppressed TSH. Ophthalmology also reviewed her as an outpatient and diagnosed mild active thyroid eye disease. On examination, she had mild bilateral mild conjunctival injection, chemosis and mild exophthalmos. Ocular motility was not restricted but was painful. Diplopia was not present and visual acuity was normal. She was initiated on regular hydrocortisone and hyaluronic acid eye drops. Despite this, her thyroid eye disease progressed and she is now currently receiving weekly intravenous methylprednisolone.

Conclusion: As TSH receptor antibodies can also be present in euthyroid and hypothyroid patients, thyroid eye disease should always be considered as a differential. If suspecting possible thyroid eye disease in patients with hypothyroidism, it is advisable to check TSH receptor antibody levels and refer to Ophthalmology.