Endocrine Abstracts

A 61-year-old lady presented to her general practitioner in July 2018 with weight loss, loose stools, hair loss, increased anxiety and dry eyes over several weeks. Blood tests revealed Graves’ thyrotoxicosis (TSH< 0.10 mU/l, (RR) 0.30-5.50 mU/l; Free T4 (fT4) 26.1 pmol/l, RR 11.5−22.7 pmol/l; Free T3 (fT3) 11.8 pmol/l, RR 0.0-7.0 pmol/l, thyroid receptor antibodies >40.0U/l, RR 0.0-1.8 U/l; thyroid peroxidase antibodies 173.0 iu/ml, RR 0.0-33.9 iu/ml). There was also evidence of mild Grave’s orbitopathy. She was commenced on carbimazole 15 mg once daily (od) and propranolol 20 mg three times daily. As thyrotoxicosis worsened, the dose of carbimazole was gradually increased to 60 mg od (December 2019-January 2020). Thyrotoxicosis did not improve (fT4 45.1 pmol/l, fT3 19.2 pmol/l), thus, a month later, aqueous iodine 1 drop three times a day (5 mg) was added first, followed by 1-month course of prednisolone 20 mg per day. No treatment response occurred, so the patient was referred for radioiodine treatment (RAI), that was delayed by the COVID-19 pandemic. In April 2020, the patient suffered an acute inferior ST elevation myocardial infarction (STEMI). This was treated with primary percutaneous coronary intervention, complicated by recurrent stent thrombosis and cardiac arrest. The patient received a 2-day course of Amiodarone to control the ventricular arrhythmias, which interestingly normalised her fT4 and fT3. The patient remained on carbimazole 60 mg od. A surgical thyroidectomy was considered a high operative risk due to the recent STEMI. A month later, the patient was re-admitted with severe congestive cardiac failure. At that time, there was evidence of new hypothyroid (fT4 4.4 pmol/l, TSH 8.10 mU/l). Thus, the dose of carbimazole was reduced to 5 mg once daily. In July 2020, a recurrence of thyrotoxicosis occurred. RAI was administered in July 2020 with 2 weeks of 30 mg per day prednisolone cover for Grave’s orbitopathy. Recurrence of thyrotoxicosis occurred as soon as the carbimazole was stopped. Carbimazole 60 mg was restarted and tapered down over the following year, until the carbimazole requirement plateaued at 15 mg/10 mg alternate days. A second radioiodine dose was administered in July 2021 and the carbimazole stopped a month later. By September 2021, the patient had developed profound hypothyroidism (TSH 76.70 mU/l, low fT4 3.8 pmol/l, fT3<3.0 pmol/l) and levothyroxine replacement was initiated. This represents a case of Grave’s disease which was resistant to treatment with carbimazole, iodine and first dose RAI. Thyrotoxicosis contributed to cardiac complications (STEMI and heart failure). Additionally, the temporary thyroid function suppression following the amiodarone clearly illustrates the Wolff-Chaikoff phenomenon.