Endocrine Abstracts

Graves’ disease (GD) is the most common cause of hyperthyroidism¹ and is caused by stimulating autoantibodies to the TSH receptor (TRAb).² TRAb assays have 98% sensitivity and 99% specificity ³ for GD and are recommended as the first-line cost-effective investigation to diagnosis the aetiology of hyperthyroidism and determine the risk of thyroid eye disease.^4,5 In TRAb antibody negative patients, radionuclide imaging may be helpful in demonstrating focal increased uptake (toxic nodular disease) or absent uptake (thyroiditis). We audited our diagnostic work-up of new cases of hyperthyroidism presenting to King’s College Hospital, London between 1 January 2018 to 30 June 2018. We identified 56 patients (48 female and 8 male); age range 20–92 years. TRAbs were measured in n=44 patients: TRAbs were elevated in n=21, measurable but within the reference range in n=8, and undetectable in n=15. Of the n=15 TRAb negative patients; n=6 had convincing clinical/biochemical evidence of a thyroiditis; n=3 demonstrated spontaneous remission of thyrotoxicosis and n=2 underwent technetium uptake scans which showed features typical of GD. N=4 patients did not attend requested imaging investigations. Of the n=8 patients with measurable but normal range TRAbs, n=2 were managed as GD, n=3 underwent technetium uptake scans which showed features typical of GD, n=2 had clinical/biochemical features suggestive of a thyroiditis and n=1 demonstrated resolution of thyrotoxicosis. N=2 patients underwent nuclear medicine imaging as a first-line diagnostic investigation to establish the aetiology of hyperthyroidism; n=1 revealed an autonomously functioning nodule and n=1 nodules with no focal autonomy. N=10 patients had neither TRAb nor nuclear medicine imaging as first line investigation; of these n=5 had evolving/sub-clinical disease, n=5 were observed. In conclusion, TRAb testing was performed first-line in 79% of new referrals for hyperthyroidism. We are working towards clinicians adopting a more consistent approach to determining the aetiology of hyperthyroidism.