Endocrine Abstracts

Transformation of Hashimoto’s thyroiditis to Graves’ disease is rare and can occur at any point during autoimmune hypothyroidism. We present a 50-year-old lady, who presented with palpitations and fatigue. Initial thyroid function tests showed hyperthyroidism with elevated thyroid peroxidase (TPO) (146.48 IU/ml, reference range 0 to 5 IU/ml) but negative TSH receptor antibodies (TRAb). Thyroid uptake scan revealed features consistent with Hashitoxicosis, and ultrasound (thyroid) demonstrated diffusely heterogeneous echotexture and features suggestive of thyroiditis. She was a non-smoker with family history of lupus. She was started on low-dose carbimazole and beta-blocker, with regular monitoring. On follow-up, TPO antibodies were elevated (654 IU/mL) and, interestingly, TSH receptor antibodies became raised (7.8 IU/L, reference range <0.4 units/ L) after 9 months. Pathophysiology of this transformation remains unclear. However, potential mechanism could be conversion or change in quantity from blocking to stimulating subtypes of TRAb. Literature review identified higher prevalence of smoking among individuals transitioning from Hashimoto thyroiditis to Graves’ disease and these switchers significantly showed higher prevalence of personal and familial history of non-thyroidal autoimmune disorders. However, our patient was a non-smoker but had family history of lupus. This case highlights Hashimoto’s thyroiditis transforming into Graves’ disease, in which TSH receptor antibody turns from negative to positive during its interesting clinical course.