FRI559 An Uncommon Association Of Two Common Etiologies Of Hyperthyroidism

Disclosure: C. Chew: None. Introduction: Subacute thyroiditis and Graves’ disease are two common etiologies of hyperthyroidism. Association of these two diseases in patient presented with recurrent hyperthyroidism has rarely been reported. Case Report: A 35 years old women, with no known medical illness, was referred to Endocrine Clinic for painful anterior neck swelling associated with palpitation for 2 weeks. The symptoms were preceded by 3 days history of sore throat and mild fever She denied other symptoms of hyperthyroidism. Her last menses was 3 weeks prior. On physical examination, she was tachycardic with heart rate of 115 beats per minute. Her blood pressure was 135/90 mmHg and she was afebrile. There was a tender and diffusely enlarged goiter. However, there were no signs of thyroid eye disease and other signs of hyperthyroidism. Examinations of her throat, lung, abdomen, cardiovascular system and neurological system were unremarkable. There was also absence of lymphadenopathy. She denied family history of thyroid disease. Results of laboratory investigations were suggestive of hyperthyroidism secondary to subacute thyroiditis: Free T4 52 pmol/L (8-16), TSH <0.01 mIU/L (0.45-4.50), TRAb 0.8 IU/L (0-1.0) and ESR 108 mm/hr (1-10). The technetium scan showed mildly enlarged gland with decreased uptake of Tc-99m tracer suggestive of thyroiditis. She was treated with Ibuprofen and Propranolol, and her symptoms improved. At 6 weeks follow up, her thyroid function normalized with Free T4 of 13 pmol/L (8-16), TSH of 1.28 mIU/L (0.45-4.50). However, she complained of weight loss and palpitation at 6 months follow up. Examination revealed a small painless diffuse goiter and she was tachycardic with heart rate of 115 beats per minute. Thyroid function test confirmed recurrence of hyperthyroidism: free T4 45.8 pmol/L (8-16) and TSH <0.01 mIU/L (0.45-4.50). Elevated TSH receptor antibody (TRAb) level at 16.8 IU/L confirmed the diagnosis of Graves’ disease. Carbimazole was then started. Discussion: Subacute thyroiditis and Graves’ disease are two common etiologies of hyperthyroidism. The incidence of association of these two diseases had been reported to be rare at 0.15% in patients with Graves’ disease and 0.76% in patients with subacute thyroiditis (1). The postulated mechanism of the association is that the release of thyroid antigens and corresponding activation of the immune system due to viral invasion of the thyroid gland in subacute thyroiditis may cause the subsequent Graves’ disease (1,2). Conclusion: Graves’ disease should be suspected in patient with persistent or recurrent hyperthyroidism after an episode of subacute thyroiditis although it is rare. Reference: 1. Nakano Y et al. Graves’ disease following subacute thyroiditis. Tohoku J. Exp. Med. 2011; 225:301-309. 2. Bartalena L et al. Graves’ disease occurring after subacute thyroiditis. Report of a case and review of the literature. Thyroid. 1996; 4:345-348. Presentation: Friday, June 16, 2023