Endocrine Abstracts

A 73-year-old gentleman due to undergo prostatectomy for adenocarcinoma was found to have biochemical secondary hyperthyroidism at a preoperative assessment. His thyroid stimulating hormone (TSH) was 5.08 µIU/ml and free T4 (fT4) was 22.7 pmol/l. He was clinically euthyroid and did not have a goitre. His past medical history was of subclinical hypothyroidism, atrial fibrillation, and hypertension. Subclinical hypothyroidism was diagnosed in 2020 based on findings of TSH 11.9 µIU/ml and fT4 16.8 pmol/l. Anti-TSH receptor and TPO antibodies were negative. He was started on levothyroxine 50 mg daily. Two weeks later, he was prescribed amiodarone 300 mg daily for management of atrial fibrillation. In 2021, he underwent catheter ablation which successfully restored sinus rhythm, yet amiodarone was continued. He has since had six measurements of elevated TSH and fT4, while remaining asymptomatic. His levothyroxine dose was reduced to 25 mg by the general practitioner. In 2023, he was diagnosed with adenocarcinoma of the prostate and he was scheduled for robotic-assisted radical prostatectomy. An endocrinologist was consulted preoperatively regarding the abnormal thyroid function tests. A diagnosis of amiodarone induced type 1 thyrotoxicosis was confirmed, three years after secondary hyperthyroidism was first noted on routine monitoring blood tests. The patient underwent successful prostatectomy. This case of three-year delay in the diagnosis of amiodarone induced type 1 thyrotoxicosis highlights the need for improved awareness of thyroid function test interpretation among clinicians, as well as integrated communication between primary and secondary care specialists.