Endocrine Abstracts

A 48-year-old gentleman was referred to the endocrine team with abnormal thyroid function tests (TFTs). His background history included cardiomyopathy complicated by atrial fibrillation (AF). He had been treated with amiodarone for a year. TFTs were monitored regularly during treatment and were normal. Four months after stopping amiodarone, he complained of weight loss, sweating and tremor. He had no family history of thyroid disease. He had a resting heart rate of 120/min (AF), warm, sweaty hands with fine tremors, lid lag but no Graves eye signs or goitre. FT4 level >77.2 pmol/l (9–19 pmol/l); TSH <0.005 mU/l (0.4–4.5 mU/l); FT3 9.1 nmol/l (0.9–2.5 nmol/l); anti-thyroid peroxidase antibodies (Anti TPO) 1 IU/ml (0–135 IU/ml); ultrasound revealed a small multinodular goitre; radioiodine uptake scan showed low uptake with only 1% retained activity after 24 h (10–25%).

The ultrasound findings were suggestive of type 1 amiodarone induced thyrotoxicosis (AIT), however low radioiodine uptake 4 months after stopping amiodarone was suggestive of type 2 AIT. He was treated with carbimazole 40 mg daily, prednisolone 40 mg and beta-blockade for both symptom relief and AF rate control. Within a week, the patient started to improve clinically and biochemically (FT4 42.1 pmol/l). He was reviewed at the outpatient clinic 3 and 6 weeks post discharge when there was further clinical and biochemical improvement (FT4 21.6 pmol/l and 15.5 pmol/l respectively). The plan is to taper the prednisolone over 3 months and to reduce the carbimazole to a low maintenance dose for 12 months.

This case illustrates the difficulty in differentiating type 1 and type 2 AIT. We suggest the term (Type 3 AIT) for cases of mixed etiology where carbimazole/prednisolone combination treatment can be effective. We also suggest baseline TFTs and Anti TPO before amiodarone therapy.